The son of a merchant, he was born at Portsmouth, Hampshire and attended school at St Paul's, Southsea, Stockwell Grammar, London and King's College London.During 1855, he was admitted as a pensioner to Christ's College, Cambridge, where he graduated in 1859 as 18th wrangler. After a year as Mathematical Master at Rossall School, Fleetwood, Lancashire and a year at Leamington College, he spent 6 years as professor of mathematics at the Royal College, Mauritius. A decrease of health compelled him to resign, and he returned to England and settled in London during 1867. From 1868 to 1885 he had the job of Secretary to the Palestine Exploration Fund. During 1871, he was admitted to Lincoln's Inn

He published during 1868 Studies in French Poetry. Three years later he began his collaboration with writer James Rice. Among their joint productions are Ready-money Mortiboy (1872), and the Golden Butterfly (1876), both, especially the latter, very successful. This association was ended by the death of Rice during 1882. Thereafter Besant continued to write voluminously by himself, his main novels being All in a Garden Fair (which Rudyard Kipling credited in Something of Myself with inspiring him to leave India and make a career as a writer), Dorothy Forster (his own favorite), Children of Gibeon, and All Sorts and Conditions of Men. The two latter belonged to a series in which he endeavored to arouse the public conscience to the sadness of life among the poorest classes of cities. In this crusade Besant had considerable success, the establishment of The People's Palace in the East of London being one result. In addition to his fiction, Besant wrote largely on the history and topography of London. His plans for this topic were left unfinished: among his books on this subject is London in the 18th Century.

Besant was a freemason, serving as Master Mason in the Marquis of Dalhousie Lodge, London from 1873. He conceived the idea of a Masonic research lodge, the Quatuor Coronati Lodge of which he was first treasurer from 1886.

He was treasurer of the 'Atlantic Union', an association which sought to improve social relations between Britons and Americans.

Fiction

• The Alabaster Box. 1900.
• Alfred. 3rd ed. 1899.
• All in a Garden Fair. 3 vols. 1883.
• All Sorts and Conditions of Men. 3 vols. 1882.
• Armorel of Lyonesse. 3 vols. 1890.
• The Bell of St. Paul's. 3 vols. 1889.
• Beyond the Dreams of Avarice. 1895.
• Blind Love. By Wilkie Collins, completed and with preface by W. Besant. 3 vols. 1890.
• By Celia’s Arbour: A tale of Portsmouth town. With James Rice. Reprinted from The Graphic. 3 vols. 1878.
• The Captains' Room etc.. 3 vols.
• The Case of Mr. Lucraft and other tales. By the authors of Ready Money Mortiboy (with James Rice). 2 vols. 1876.
• The Changeling. 1898.
• The Chaplain of the Fleet. With James Rice 3 vols. 1881.
• Children of Gibeon. 2nd ed. 3 vols. 1886.
• The City of Refuge. 3 vols. 1896.
• Dorothy Forster. 3 vols. 1884.
• Doubts of Dives. [Speculative fiction in which a rich and poor man exchange bodies].
• A Five Years' Tryst and other stories. 1902.
• For Britain's Soldiers. By W.L. Alden, Sir W. Besant etc., with preface by C.J.C. Hyne. 1900.
• For Faith and Freedom. 3 vols. 1889.
• A Fountain Sealed. 1897.
• The Fourth Generation. 1900.
• The Golden Butterfly. With James Rice. 3 vols. 1876.
• Herr Paulus. 3 vols. 1888.
• The Holy Rose &c. 1890.
• In Deacon's Orders &c. 1895.
• The Ivory Gate. 3 vols. 1893.
• The Lady of Lynn. 1901.
• The Master Craftsman. 2 vols. 1896.
• The Monks of Thelema. With James Rice. 3 vols. 1878.
• My Little Girl. By the authors of Ready-money Mortiboy. With James Rice. 3 vols. 1873.
• No Other Way. 1902.
• The Orange Girl. 1899.
• Ready-Money Mortiboy. Repr. from Once a Week. With James Rice. 3 vols. 1872. Repr. of 1885 ed. Bath, 1974.
• The Rebel Queen. 3 vols. 1893.
• The Revolt of Man. 1882. [Speculative fiction: traditional roles of sexes are reversed].
• St. Katherine's by the Tower. 3 vols. 1891.
• The Seamy Side. With James Rice. 3 vols. 2nd. ed. 1880.
• The Ten Years' Tenant and other stories. With James Rice. 3 vols.
• This Son of Vulcan. By the authors of Ready-Money Mortiboy. With James Rice. 3 vols. 1876.
• To Call Her Mine &c. 1889.
• "Twas in Trafalgar's Bay" and other stories. With James Rice. 2nd ed. 1879.
• Uncle Jack &c. 1885.
• Verbena, Camellia, Stephanotis, &c. 1892.
• With Harp and Crown. By the authors of “Ready-Money Mortiboy.” With James Rice. 3 vols. 1875.
• The World Went Very Well Then. 3 vols. 1887.

Collected editions (fiction)

Novels by W.B. and James Rice. Library ed. 10 vols. 1887—88. Comprising in sequence Ready-Money Mortiboy, This Son of Vulcan, With Harp and Crown, The Golden Butterfly, By Celia’s Arbour, The Seamy Side, The Chaplain of the Fleet, The Case of Mr. Lucraft and Other Tales, ‘Twas in Trafalgar’s Bay and Other Stories, The Ten Years’ Tenant and Other Stories [My Little Girl, The Monks of Thelema apparently missing from this series].

Plays

• The Charm and other drawing-room plays. With W. Pollock. 1896.

General non-fiction [excluding items on London]

• "The Amusements of the People", Contemporary Review 45 (1884): 342-53.
• William Tuckwell, Art and hand work for the people, being three papers read before the Social Science Congress, Sept. 1884. By W.T., C. G. Leland, and W. Besant. Manchester, 1885.
• The Art of Fiction: A Lecture Delivered at the Royal Institution on Friday Evening, April 25, 1884. 1884. New ed., 1902.
• As we are and as we may be. 1903.
• Autobiography. With prefatory note by S. Squire Sprigge. Hutchinson, 1902.
• Bourbon' journal, August 1863. 1933.
• Captain Cook. English Men of Action. 1890.
• Constantinople. A sketch of its history from its foundation to its conquest by the Turks in 1453. By W.J.B. and Walter Besant. 1879.
• Essays and Historiettes. 1903.
• The Eulogy of Richard Jefferies. 1888.
• Fifty Years Ago. 1888.
• The French Humourists from the 12th to the 19th century. 1873.
• Gaspard de Coligny. The New Plutarch. 1879. New ed. 1894.
• Jerusalem, the City of Herod and Saladin. By W.B. and E.H. Palmer. 1871.
• The Life and Achievements of Edward Henry Palmer. 1883.
• The Pen and the Book. 1899.
• "The People’s Palace", Contemporary Review 51 (1887): 226-33.
• The Queen’s Reign and its commemoration. 1897.
• Sir Richard Whittington, Lord Mayor of London. With James Rice. The New Plutarch. 1881. New ed. 1894.
• The Story of King Alfred. [1912].
• Studies in Early French Poetry. 1868.

Selected Books on London [volumes in the 10-volume Survey of London published by A & C. Black are included under their individual volume titles and marked with an asterisk]

• East London. 1901.
• Early London: prehistoric, Roman, Saxon, and Norman. 1908.*
• Holborn and Bloomsbury. With G. E. Mitton. Fascination of London series. 1903.
• London. 1892.
• London. City. 1910.*
• London in the Eighteenth Century. 1902.*
• London in the Nineteenth Century. 1909.*
• London in the Time of the Stuarts. 1903.*
• London in the Time of the Tudors. 1904.*
• London, North of the Thames. 1911.*
• London, South of the Thames. 1912.*
• Medieval London. 2 vols. 1906.**
• Shoreditch and the East End. With others. Fascination of London series. 1908.
• South London. 1899.
• The Strand District. With G. E. Mitton. Fascination of London series. Repr. with corrections. 1903.
• The Thames. Fascination of London series. 1903.
• Westminster. 1895.