Pierre de Villiers Pienaar (1904–1978) was a South African Afrikaans academic and Professor at University of the Witwatersrand (Wits) and later at University of Pretoria, who pioneered Speech Language Therapy in South Africa and specialising in Audiology and Lexicography as well as being an Afrikaans author. As Lexicographer in 1973, he was part of the group of authors that established the Afrikaans Explanatory Dictionary ("Afrikaans Verklarende Woordeboek") alongside Prof M.S.B. Kritzinger and Prof F.J. Labuschagne.