R. G. Howarth was educated at Fort Street Boys' High School. In 1929 he graduated from the University of Sydney with several distinctions, including the Wentworth travelling scholarship. Graduating from Oxford University with a Bachelor of Letters majoring in seventeenth century poetry, he returned to the University of Sydney in 1933 as a lecturer.
Howarth quickly established an international reputation as an expert in Elizabethan tragedy and Restoration comedy, but he attracted attention locally for introducing his students to modern writers such as James Joyce and T. S. Eliot, and Australian writers such as Joseph Furphy and Kenneth Slessor. Howarth played an important part in the study of Australian literature during the 1940s and 1950s by founding and editing Southerly, a periodical in which works of Australian literature attracted serious critique. Howarth contributed his own literary criticism to Southerly and the Sydney Morning Herald and continued his scholarly work with anthologies and editions of poetry, fiction and letters, raising the profile of Australian writers and their works.
In 1948 Howarth was appointed Reader in English Literature and during the 1950s was active in many committees and literary societies. He was president of the Sydney branch of the English Association (1947-1955), elected a fellow of the Royal Society of Literature of the United Kingdom in 1952, a member of the Commonwealth Literary Fund (1950-1955) and was a founding member of the Australian Humanities Research Council (1954 -1955). From 1955-1971, he was Professor of English Literature at the University of Cape Town.
In the early 1970s, having been awarded grants by the Commonwealth Literary Fund, Howarth returned to Australia to compile an edition of Norman Lindsay's letters, but died before finishing the project. The edition was completed by Anthony Barker in 1979. Howarth married twice and was survived by two sons. The Oxford Companion to Australian Literature asserts he was 'widely acknowledged by contemporaries as one of Australia's finest literary scholars'.