Wilhelm Heinrich Immanuel Bleek (8 March 1827 – 17 August 1875) was a German linguist who lived in the Cape Colony and developed a particular interest for the languages and culture of the San people. He is the author of A Comparative Grammar of South African Languages. His great project, jointly executed with Lucy Lloyd in collaboration with San individuals who came to stay at his house for months or years, is the Bleek and Lloyd Archive of ǀxam and ǃkun texts, which has been listed on UNESCO's Memory of the World register. A collection of these texts eventually reached press with Specimens of Bushman Folklore. Bleek was influenced by scientific racism and this is reflected in some of his scientific practices and theories.

Wilhelm Heinrich Immanuel Bleek was born in Berlin on 8 March 1827. He was the eldest son of Friedrich Bleek, Professor of Theology at Berlin University and then at the University of Bonn, and Auguste Charlotte Marianne Henriette Sethe. He was also the cousin of zoologist Ernst Haeckel, one of the great promoters of scientific racism in Germany. Bleek graduated from the University of Bonn in 1851 with a doctorate in linguistics, after a period in Berlin where he went to study Hebrew and where he first became interested in African languages. Bleek's thesis featured an attempt to link North African and Khoikhoi (or what were then called Hottentot) languages – the thinking at the time being that all African languages were connected. After graduating in Bonn, Bleek returned to Berlin and worked with a zoologist, Dr Wilhelm K H Peters, editing vocabularies of East African languages. His interest in African languages was further developed during 1852 and 1853 by learning Egyptian Arabic from Professor Karl Richard Lepsius, whom he met in Berlin in 1852.

Bleek was appointed official linguist to Dr William Balfour Baikie's Niger Tshadda Expedition in 1854. Ill-health (a tropical fever) forced his return to England where he met George Grey and John William Colenso, the Anglican Bishop of Natal, who invited Bleek to join him in Natal in 1855 to help compile a Zulu grammar. After completing Colenso's project, Bleek travelled to Cape Town in 1857 to catalogue Sir George Grey's vast private library. Grey had philological interests and was Bleek's patron during his time as Governor of the Cape. The two had a good professional and personal relationship based on an admiration that appears to have been mutual. Bleek was widely respected as a philologist, particularly in the Cape. While working for Grey he continued with his philological research and contributed to various publications during the late 1850s. Bleek requested examples of African literature from missionaries and travellers, such as the Revd W Kronlein who provided Bleek with Namaqua texts in 1861.

In 1859 Bleek briefly returned to Europe in an effort to improve his poor health but returned to the Cape and his research soon after. In 1861 Bleek met his future wife, Jemima Lloyd, at the boarding house where he lived in Cape Town (run by a Mrs Roesch), while she was waiting for a passage to England, and they developed a relationship through correspondence. She returned to Cape Town from England the following year.

Bleek married Jemima Lloyd on 22 November 1862. After living in central Cape Town, the Bleeks settled in the then still rural area of Mowbray in 1866. There, they first lived at The Hill but moved in 1875 to Charlton House. Jemima's sister, Lucy Lloyd, joined the household in the late 1860s, became his colleague, and carried on his work after his death.

When Grey was appointed Governor of New Zealand in November 1861, he presented his collection to the National Library of South Africa on condition that Bleek be its curator, a position he occupied from 1862 until his death in 1875. In addition to this work, Bleek supported himself and his family by writing regularly for Het Volksblad throughout the 1860s and publishing the first part of his A Comparative Grammar of South African Languages in London in 1862. The second part was also published in London in 1869 with the first chapter appearing in manuscript form in Cape Town in 1865. Unfortunately, much of Bleek's working life in the Cape, like that of his sister-in-law after him, was characterised by extreme financial hardship which made his research even more difficult to continue with.

Bleek's first contact with San people (Bushmen) was with prisoners at Robben Island and the Cape Town Gaol and House of Correction, in 1857. He conducted interviews with a few of these prisoners, which he used in later publications. These people all came from the Burgersdorp and Colesberg regions and spoke variations of one similar-sounding "Bushman" language. Bleek was particularly keen to learn more about this "Bushman" language and compare it to examples of "Bushman" vocabulary and language earlier noted by Hinrich Lichtenstein and obtained from missionaries at the turn of the 19th century.

In 1863 resident magistrate Louis Anthing introduced the first ǀXam-speakers to Bleek. He brought three men to Cape Town from the Kenhardt district to stand trial for attacks on farmers (the prosecution was eventually waived by the Attorney General). In 1866 two San prisoners from the Achterveldt near Calvinia were transferred from the Breakwater prison to the Cape Town prison, making it easier for Bleek to meet them. With their help, Bleek compiled a list of words and sentences and an alphabetical vocabulary. Most of these words and sentences were provided by Adam Kleinhardt (see Bleek I-1, UCT A1.4.1).