Selby Msimang was born on 13 December 1886 in Edendale, Pietermaritzburg. He and his elder brother, Richard Msimang,were born to Joel Msimang and his wife Joanah Radebe. Joel Msimang was a well-known African preacher who founded the Independent Methodist Church.
Msimang Selby received his primary education at the Emakosini Primary School in Nhlangano, Swaziland. Between 1903 and 1907 he studied first at Kilnerton Institution, a Methodist college in Pretoria, then Edendale Institution at Edendale, and finally at Healdtown Institution, a Methodist boarding school near Fort Beaufort in the Eastern Cape. Though he was then a qualified teacher, he never taught. His career started in 1908 when he was appointed as interpreter in Germiston, Transvaal. He never stayed in any career for long but kept changing jobs and homes. Between 1908 and 1965 he had fifteen occupations and lived in ten towns or cities in three provinces (the Transvaal, the Orange Free State and Natal). From 1942, however, he settled in Edendale near Pietermaritzburg.
His political career started in 1912 when he was a founder member of the South African Native National Congress (SANNC, African National Congress (ANC) after 1923). During the following 30 years he participated in a number of their meetings, deputations and other activities. For many years he under-took the labour portfolio of the congress, and was a prominent member of the committee established to raise funds to send a deputation to Britain to try to have the Natives Land Act of 1913 repealed.
In Bloemfontein, in 1917, he was the editor of a newspaper (Morumioa- Inxusa- Messenger) the title of the newspaper varied which only existed for two years. It could not be established if a connection existed between this newspaper and the one with which D.S. Letanka was involved in 1911, i.e. Moromioa. During his stay in Bloemfontein (1917-1922) his long relationship with the labour movement started when, as a labour organiser, he led a strike of municipal workers in Bloemfontein in 1917, for which he was arrested and detained. In 1919 he liaised with Clements Kadalie, founder of the Industrial and Commercial Workers' Union (ICU), about the organisation of African workers. Together they planned the establishment of a national ICU and in 1920 held a meeting in Bloemfontein with this in mind. Msimang was elected president of the national ICU. When Kadalie failed to be elected to the executive he withdrew with his supporters. This led to increasing animosity between Msimang and Kadalie, resulting in Msimang's resignation as president and distancing himself from the ICU until after Kadalie's resignation in 1929. Msimang then rejoined and during the decline of the ICU he held the post of national propagandist. From 1928 to 1937 Msimang was a labour advisor in Johannesburg.
In 1922 Msimang returned to Johannesburg and became a member of the Joint Council for Europeans and Bantu. He was still involved in the activities of the SANNC/ANC and served on the national executive committee of the ANC during the terms of office of presidents J.T. Gumede (1927-1930) and Pixley Seme (1930-1937). In 1932 he was a member of the so-called revival committee that wanted to strengthen the organisation from within to prevent its stagnation. Three years later, during the first meeting of the All-African Convention (AAC) in Bloemfontein in December 1935, he was elected as secretary. In 1942 he returned to Natal and was elected provincial secretary of the Natal branch of the ANC, a position he retained until 1956. He was also a confidant of the Natal leader A.W.G. Champion.
In 1948 he became a member of the Native Representative Council (NRC) although at that time it was no longer an active body. In December of the same year he attended the discussions with the AAC as delegate of the ANC during an unsuccessful attempt to reconcile these two organisations. During the annual congress of the ANC of that year Msimang was elected to the committee which had to draw up the Programme of Action. Early in 1949 he represented the ANC in discussions with prominent Indian leaders in an effort to reconcile Africans and Indians after bloody clashes between them in Durban and surrounding areas in January 1949. A year later Msimang and Champion's political ways parted and Msimang lost his position in the ANC. However, when Chief Albert Luthuli defeated Champion as president of the ANC in 1951, Msimang was reinstated as provincial secretary. But he lost interest in the ANC and even before the Defiance Campaign of 1952 he resigned as provincial secretary in Natal.
In 1953 Msimang became a founder member of the multiracial Liberal Party of South Africa. From 1956-1968 he served on the executive committee and in due course became the national vice-chairperson. His activities were, however, hampered in 1965 when the government forbade him to attend meetings for five years.
Msimang was also interested and active in local politics and problems. For many years from 1942 he was secretary of the Edendale Advisory Board Local Health Commission. He was the founder of the Edendale Benevolent Society and served as its secretary from 1946 to 1952, and from 1967 as honorary life president. In 1973 he was elected secretary of the Edendale AmaKholwa Tribe. In 1975 Msimang became a member of the national council of the Inkatha yeNkululeko yeSizwe. From 1974 to 1975 he served on the executive committee of the South African Institute of Race Relations (SAIRR). He was a Methodist and served in various committees of the church.
Msimang was a prolific author. Apart from numerous newspaper articles, including series of articles in several newspapers, he published a pamphlet The crisis in Johannesburg in 1936 about the effect of the 1936 Land Act on Africans. He was married twice and had four sons and four daughters. His first wife was Mercy Mahlomola King whom he married in July 1913.
She died in September 1951, and in August 1952 he married Miriam Primrose Oldjohn. He died on 29 March 1982