For publishing purposes, I created a database of hundreds of missionary biographies. Here are links to the 183 of them that are available for free online. Several websites assisted in the creation of this list, especially the Internet Archive, missiology.org.uk, and Wholesome Words.

NORTH AMERICA

The Parish of the Pines by Thomas D. Whittles (1873-?)

Canada
The Harvest of the Sea: A Tale of Both Sides of the Atlantic by Sir Wilfred Thomason Grenfell (1865-1940)
Adrift on an Ice-Pan by Sir Wilfred Thomason Grenfell (1865-1940)

Greenland
Amid Greenland Snows: The Early History of Arctic Missions by Jesse Page (1805-1883)

Jamaica
Memoir of William Knibb: Missionary in Jamaica by John Howard Hinton (1791-1873)

Missions among Native Americans
An Historical Account of the Incorporated Society for the Propagation of the Gospel in Foreign Parts: Containing Their Foundation, Proceedings and the Success of Their Missionaries in the British Colonies to the Year 1728 by David Humphreys (1689-1740)
A journal of the life, gospel labours, and Christian experiences, of that faithful minister of Jesus Christ, John Woolman by John Woolman (1720-1772)
The Triumph of the Reformed Religion in America: The Life of the Renowned John Eliot by Cotton Mather (1663-1728)
An Account of the Life of the Late Rev. David Brainerd by Jonathan Edwards (1703-1758)
By Canoe and Dog-Train: Among the Cree and Salteaux Indians by Egerton Ryerson Young (1840-1909)
On the Indian Trail: Stories of Missionary Work among the Cree and Salteaux Indians by Egerton Ryerson Young (1840-1909)
Stories from Indian Wigwams and Northern Camp-Fires by Egerton Ryerson Young (1840-1909)
Oowikapun: Or, How the Gospel Reached the Nelson River Indians by Egerton Ryerson Young (1840-1909)
Indian Life in the Great North-West by Egerton Ryerson Young (1840-1909)
The Battle of the Bears: Life in the North Land by Egerton Ryerson Young (1840-1909)
The Apostle of the North: Rev. James Evans by Egerton Ryerson Young (1840-1909)
Mirabilia Dei Inter Indicos, or, The Rise and Progress of a Remarkable Work of Grace amongst a Number of the Indians in the Provinces of New-Jersey and Pennsylvania, Justly Representied in a Journal Kept by Order of the Honourable Society (in Scotland) for Propagating Christian Knowledge by David Brainerd (1718-1747)
Memoirs of the Rev. David Brainerd by Jonathan Edwards (1703-1758), David Brainerd (1718-1747), Sereno Edwards Dwight (1786-1850)
David Brainerd, the Apostle of the North American Indians by Jesse Page (1805-1883)
Brief Narrative of the Progress of the Gospel amongst the Indians in New England, in the Year 1670 by John Eliot (1604-1690)

CENTRAL AND SOUTH AMERICA

A Voice from South America by Captain Allen Francis Gardiner (1794-1851)
South America: The Dark Continent by Emilio Olsson

Argentina
Captain Allen Gardiner of Patagonia: The Dauntless Sailor Missionary by Jesse Page (1805-1883)
The Story of Commander Allen Gardiner by John William Marsh (1822-1882), Waite H. Stirling

Brazil
A Thousand Miles in a Dug-Out: Being the Narrative of a Journey of Investigation among the Red-Skin Indians of Central Brazil by Frederick Charles Glass (1871-1960)
Adventures with the Bible in Brazil by Frederick Charles Glass (1871-1960)

Guyana
In the Tropics: Scenes and Incidents of West Indian Life by Jabez Marrat (1833-1909)

EASTERN EUROPE

Memoir of Mrs. Stallybrass, Wife of the Rev. Edward Stallybrass, Missionary to Siberia by Edward Stallybrass
Jonas King: Missionary to Syria and Greece by F. E. H. Haines

AFRICA

The Flaming Torch in Darkest Africa by William Taylor (1821-1902)
Africa Waiting or The Problem of Africa’s Evangelisation by Douglas Montagu Thornton (1873-1907)
Back to the Long Grass: My Link with Livingstone by Daniel Crawford (1870-1926)
Missionary Travels and Researches in South Africa by David Livingstone (1813-1873)
Narrative of an Expedition to the Zambesi and Its Tributaries and of the Discovery of the Lakes Shirwa and Nyassa by David Livingstone (1813-1873)
The Last Journals of David Livingstone in Central Africa by Horace Waller
Journal of an Expedition to Explore the Course and Termination of the Niger; with a Narrative of a Voyage Down That River to Its Termination by Richard Lander, John Lander
Central Africa Revisited: A 16,000 Mile Tour Thoughout the Fields of the Africa Inland Mission in Kenya, Tanganyika, Uganda, Congo, Sudan and Egypt by Daniel Morison Miller (1888-1965)
Garenganze; or, Seven Years Pioneer Mission Work in Central Africa by Frederick Stanley Arnot (1858-1914)
The Life and Explorations of Frederick Stanley Arnot, F.R.G.S. by Ernest Baker
The Personal Life of David Livingstone: Chiefly from his Unpublished Journals and Correspondence in the Possession of His Family by William Garden Blaikie (1820-1899)

Cameroon
Alfred Saker: The Pioneer of the Cameroons by Emily Martha Saker (b. 1849)

Congo River Region
Pioneering on the Congo by William Holman Bentley (1855-1905)
Life on the Congo by William Holman Bentley (1855-1905)
W. Holman Bentley: The Life and Labours of a Congo Pioneer, By His Widow by H. M. Bentley

Ethiopia
John Ludwig Krapf: Explorer-Missionary of Northeastern Africa by Paul Edward Kretzmann (1883-1965)
Eclipse in Ethiopia and Its Corona Glory by Esmé Ritchie Rice

Kenya
In the Heart of Savagedom: Reminiscences of Life and Adventure during a Quarter of a Century of Pioneering Missionary Labours in the Wilds of East Equatorial Africa by Eva Stuart Watt

Madagascar
Through Lands That Were Dark. Being a Record of a Year’s Missionary Journey in Africa and Madagascar by F. H. Hawkins (1863-1936)
Madagascar: Its Mission and Its Martyrs by Ebenezer Prout
The Martyrs’ Isle: or, Madagascar: The Country, the People, and the Missions by Annie Sharman

Malawi
The Life of Robert Laws of Livingstonia by William Pringle Livingstone (b. 1864)
Reminiscences of Livingstonia by Robert Laws (1851-1934)
Streams in the Desert: A Picture of Life in Livingstonia by James Horne Morrison (1872-1947)

Nigeria
The Romance of the Black River: The Story of the C.M.S. Nigeria Mission by F. Deaville Walker

Sierra Leone
Seven Years in Sierra Leone by Arthur Tappan Pierson (1837-1911)

South Africa & Botswana
Narrative of a Journey to the Zoolu Country, in South Africa by Captain Allen Francis Gardiner (1794-1851)
Christina Forsyth of Fingoland: The Story of the Loneliest Woman in Africa by William Pringle Livingstone (b. 1864)
Missionary Labors and Scenes in Southern Africa by Robert Moffat (1795-1883)
Robert Moffat: African Missionary by Jabez Marrat (1833-1909)
Stewart of Lovedale by James Wells
Dawn in the Dark Continent by James Stewart (1831-1905)

South Sudan
New Frontiers in the Central Sudan by C. Gordon Beacham
Seven Sevens of Years and a Jubilee: The Story of the Sudan Interior Mission by Rowland V. Bingham (1872-1942)

Uganda
Two Kings of Uganda by Robert Pickering Ashe (1857-1944)
The Last Journals of Bishop Hannington by Edwin Collas Dawson (1849-1925)
James Hannington, First Bishop of Eastern Equatorial Africa: A History of His Life and Work (1847-1885) by Edwin Collas Dawson (1849-1925)
Bishop Hannington and the Story of the Uganda Mission by William Grinton Berry (1873-1926)
Mackay of the Great Lake by Constance Evelyn Padwick (1886- )
Mackay of Uganda: The Missionary Engineer by Mary Yule
Uganda’s White Man of Work by Sophia Blanche Lyon Fahs (b. 1876)
Chronicles of Uganda by Robert Pickering Ashe (1857-1944)

Zimbabwe (Rhodesia)
Christians of the Copperbelt: The Growth of the Church in Northern Rhodesia by John Vernon Taylor
The Way of the White Fields in Rhodesia: A Survey of Christian Enterprise in Northern and Southern Rhodesia by Edwin W. Smith (1876-1957)

MIDDLE EAST AND NORTH AFRICA

Kamil Abdul Messiah by Kamil Abdulmasih (d. 1892)

North Africa
The Gospel in North Africa by John Rutherford (1816-1866)
I. Lilias Trotter, Founder of the Algiers Mission Band by Blanche Anne Frances Pigott (1849-1930)
Pioneering in Morocco: A Record of Seven Years’ Medical Mission Work in the Palace and the Hut by Robert Kerr (d. 1918)

Egypt & Sudan
A Master-Builder on the Nile: Being a Record of the Life and Aims of John Hogg, Christian Missionary by Rena L. Hogg
Douglas M. Thornton: A Study in Missionary Ideals and Methods by William Henry Temple Gairdner (1873-1928)
W.H.T.G. to His Friends by William Henry Temple Gairdner (1873-1928)
The Changing Sudan by W. Wilson Cash
The Sudan: A Short Compendium of Facts and Figures about the Land of Darkness by H. Karl Kumm (1874-1930)

Iraq & the Gulf
The History of the Arabian Mission by Alfred DeWitt Mason

Levant (Jordan, Lebanon, Syria, etc.)
Christian Researches in the Mediterrannean, from 1815 to 1820, in Furtherance of the Objects of the Church Missionary Society by William Jowett, James Connor
The Life and Correspondence of Thomas Valpy French by Herbert Alfred Birks
Lethaby of Moab: A Record of Missionary Adventure, Peril and Toil by Thomas Durley
Ventures among the Arabs: 13 Years of Pioneer Missionary Life in Arabia by Archibald Forder (1863-1934)
Fifty-Three Years in Syria: The Autobiography of Henry H. Jessup by Henry Harris Jessup (1832-1910)
Bible Works in Bible Lands: or, Events in the History of the Syria Mission by Isaac Bird (1793-1876)
Memoir of the Rev. Pliny Fisk by Alvan Bond (1793-1882)
Raymund Lull: First Missionary to the Moslems by Samuel Marinus Zwemer (1867-1952)

Yemen
Memorials of the Hon. Ion Keith-Falconer by Robert Sinker (1838-1913)

CENTRAL ASIA

Journals and Letters of the Rev. Henry Martyn by S. Wilberforce
A Memoir of the Rev. Henry Martyn by John Sargent (1780-1833)
Henry Martyn of India and Persia by Jesse Page (1805-1883)

SOUTH ASIA

Bangladesh
Bengal as a Field of Missions by Mrs. MacLeod Wylie

India
The Cobra’s Den by Jacob Chamberlain (1835-1908)
Men of Might in India Missions: Their Leaders and Their Epochs, 1706-1899 by Helen Harriet Holcomb
Life and Times of Carey, Marshman and Ward by John Clark Marshman (1794-1877)
History of the Tranquebar Mission by Johannes Ferdinand Fenger (1805-1861)
In the Tiger Jungle and Other Stories of Missionary Work among the Telugus of India by Jacob Chamberlain (1835-1908)
Biographical Sketches of Joshua Marshman by John Fenwick
Things As They Are: Mission Work in Southern India by Amy Carmichael (1867-1951)
A Memoir of Mrs. Margaret Wilson by John Wilson (1804-1875)
Memoir of William Carey by Eustace Carey
The Missionary’s Wife, or, A Brief Account of Mrs. Loveless of Madras; the First American Missionary to Foreign Lands by Richard Knill
Travels in North India by John Cameron Lowrie (1808-1900)
Two Years in Upper India by John Cameron Lowrie (1808-1900)
Two Standard Bearers in the East: Sketches of Dr. Duff and Dr. Wilson by Jabez Marrat (1833-1909)
Memoirs of Mrs. Louisa A. Lowrie : wife of the Rev. John C. Lowrie, missionary to Northern India, who died at Calcutta, Nov. 21st, 1833, aged 24 years by Ashbel Green Fairchild (1795-1864)

Pakistan
An Heroic Bishop: The Life-Story of French of Lahore by Eugene Stock (1836-1928)
Robert Clark of the Panjab: Pioneer and Missionary Statesman by Henry Martyn Clark (1857-1916)

Sri Lanka (formerly Ceylon)
One Hundred Years in Ceylon: The Centenary Volume of the Church Missionary Society in Ceylon 1818-1918 by John William Balding
Extracts from the Journal and Correspondence of the Late Mrs. M. M. Clough, Wife of the Rev. Benjamin Clough, Missionary in Ceylon by Adam Clarke, Benjamin Clough, Margaret Morley Clough (1803-1827)
Memoirs of Mrs. Elizabeth Harvard Late of the Wesleyan Mission to Ceylon and India with Extracts from Her Diary and Correspondence by William Martin Harvard

NORTHEAST ASIA

Journal of Three Voyages along the Coast of China in 1831, 1832, and 1833, with Notices of Siam, Corea, and the Loo-Choo Islands by Charles Gutzlaff
A Sound of Abundance of Rain by Campbell Naismith Moody (1866-1940)
The War and Missions in the East by A. J. MacDonald (1887-1959)

China
Not Unto Us: A Record of Twenty-One Years’ Missionary Service by Harry Grattan Guinness (1835-1910)
Memoir of William C. Burns, Missionary to China by Islay Burns (1817-1872)
Memoir of the Life and Brief Ministry of the Rev. David Sandeman, Missionary to China by Andrew Alexander Bonar (1810-1892)
A Retrospect by James Hudson Taylor (1832-1905)
Three Decades of the China Inland Mission, 1865-1895 by James Hudson Taylor (1832-1905)
Hudson Taylor and the China Inland Mission: The Growth of a Soul by Howard Taylor
The Jubilee Story of the China Inland Mission with Portraits and Map by Marshall Broomhall (1866-1937)
Hudson Taylor and the China Inland Mission: The Growth of a Work of God by Howard Taylor

Japan
A Maker of New Japan: Joseph Hardy Neesima, President of Doshisha University, Kyoto by Jerome Dean Davis (1838-1910)
Life and Letters of Joseph Hardy Neesima by Arthur Sherburne Hardy

Mongolia
More about the Mongols by James Gilmour (1843-1891)
James Gilmour of Mongolia by James Gilmour (1843-1891), Richard Lovett (1851-1904)

Taiwan (formerly Formosa)
The Saints of Formosa by Campbell Naismith Moody (1866-1940)
The Heathen Heart: An Account of the Reception of the Gospel among the Chinese of Formosa by Campbell Naismith Moody (1866-1940)

Tibet
With the Tibetans in Tent and Temple by Susanna Carson “Susie” Rijnhart (1868-1908)

SOUTHEAST ASIA

Myanmar (formerly Burma)
The Gospel in Burma by Mrs. MacLeod Wylie
An Account of the American Baptist Mission to the Burman Empire by Ann Hasseltine Judson (1789-1826)
Memoir of the Life and Labors of the Rev. Adoniram Judson by Francis Wayland
The Apostle of Burma: A Memoir of Adoniram Judson, D.D. by Jabez Marrat (1833-1909)

SOUTH PACIFIC

Heroes of the South Seas by Martha Burr Banks
Memoir of Mrs. Mary Mercy Ellis, Wife of Rev. William Ellis, Missionary in the South Seas and Foreign Secretary of the London Missionary Society by William Ellis (1794-1872)
John Williams, the Shipbuilder by Basil Joseph Mathews (1879-1951)
A Narrative of Missionary Enterprise in the South Sea Islands by John Williams (1796-1839)
Memoirs of the Rev. John Williams, Missionary to Polynesia by Ebenezer Prout

Fiji
James Calvert: or, From Dark to Dawn in Fiji by R. Vernon
James Calvert of Fiji by George Stringer Rowe (1830-1913)
The Story of Fiji by James Calvert (1813-1892)
Memoir of Mary Calvert by George Stringer Rowe (1830-1913)
The Life of John Hunt, Missionary to the Cannibals by George Stringer Rowe (1830-1913)
John Hunt: Pioneer Missionary and Saint by Joseph Nettleton
Fiji and the Fijians by James Calvert (1813-1892), Thomas Williams (1815-1891), George Stringer Rowe (1830-1913)

New Zealand
Bishop Selwyn of New Zealand, and of Lichfield: A Sketch of His Life and Work with Some Further Gleanings from His Letters, Sermons, and Speeches by George Herbert Curteis (1824-1894)
Among the Maoris; or, Daybreak in New Zealand: A Record of the Labours of Samuel Marsden, Bishop Selwyn, and Others by Jesse Page (1805-1883)
Memoirs of the life and labours of the Rev. Samuel Marsden, of Parramatta, Senior Chaplain of New South Wales: and of his early connexion with the missions to New Zealand and Tahiti by John Buxton Marsden (1803-1870)
A Short Account of the Character and Labours of the Rev. S. Marsden by William Woolls
Narrative of a Voyage to New Zealand, performed in the years 1814 and 1815, in company with the Rev. S. Marsden by John Liddiard Nicholas

New Guinea
James Chalmers: Missionary and Explorer of Rarotonga and New Guinea by William Robson
Tamate: The Life and Adventures of a Christian Hero by Richard Lovett (1851-1904)
Greatheart of Papua: James Chalmers by W. P. Nairne
These Thirty Years: The Story of the RBMU by Harry Guinness (1835-1910)
Bishop Patteson: Martyr of Melanesia by Jesse Page (1805-1883)
Life of John Coleridge Patteson, Missionary Bishop of the Melanesian Islands by Charlotte Mary Yonge (1823-1901)

Tonga & French Polynesia
Tonga and the Friendly Islands by Sarah Stock Farmer

Vanuatu (formerly New Hebrides)
The Story of John G. Paton: Thirty Years with South Sea Cannibals by John Gibson Paton (1824-1907)
Saints and Savages: The Story of Five Years in the New Hebrides by Robert Lamb

COMPILATIONS

Memoirs of British Female Missionaries by Thomas Timpson (1790-1860)
The Unoccupied Mission Fields of Africa and Asia by Samuel Marinus Zwemer (1867-1952)
A History of Moravian Missions by Joseph Edmund Hutton (1838-1937)
Moravian Missions: Twelve Lectures by Augustus C. Thompson (1812-1901)
A History of Wesleyan Missions in All Parts of the World from Their Commencement to the Present Time by William Moister (1808-1891)
An Enquiry into the Obligations of Christians to Use Means for the Conversion of the Heathens in Which the State of the Different Nations of the World, the Success of Former Undertakings, and the Practicability of Further Undertakings, Are Considered by William Carey (1761-1834)
Conquests of the Cross: A Record of Missionary Work throughout the World by Edwin Hodder (1837-1904)
The History of the Church MIssionary Society: Its Environment, Its Men and Its Work by Eugene Stock (1836-1928)
The Romance of Missionary Heroism: True Stories of the Intrepid Bravery and Stirring Adventures of Missionaries with Uncivilized Man, Wild Beasts and the Forces of Nature in All Parts of the World by John Chisholm Lambert (1857-1917)
A History of Christian Missions during the Middle Ages by George Frederick Maclear (1833-1902)
The Advance Guard: 200 Years of Moravian Missions, 1732-1932 by Anonymous
Memories of the Mission Field by Christine Isabel Tinling (1869-1943)
Journal of Voyages and Travels by Daniel Tyerman, George Bonnet
Twelve Mighty Missionaries by Esthme Ethelind Enock (1874-1947)
Heroes of Missionary Enterprise by Claud Field
Giants of the Missionary Trail: The Life Stories of Eight Men Who Defied Death and Demons by Eugene Myers Harrison
The Missionary Heroes of Africa by James Horne Morrison (1872-1947)
Three Martyrs of the Nineteenth Century by Elizabeth Rundle Charles (1828-1896)
On the Trail of the Pioneers: A Sketch of the Missions of the United Free Church of Scotland by James Horne Morrison (1872-1947)

Region classifications are based on those used by the Joshua Project.