Theophilus "Theo" Verster (born 14 January 1975) is a South African former swimmer, who specialised in butterfly and in individual medley events.

He also held an African record of 55.04 from the 2002 Telkom International Sprint Challenge that defeated Terence Parkin for a top finish and sliced off Brendon Dedekind's standard by 0.37 of a second.

Verster ascended to prominence in the global scene at the 1999 Pan Pacific Swimming Championships in Sydney, placing seventh each in the 100 m butterfly (54.28) and 200 m individual medley (2:04.24).

[3][4] On that same year, at the All-Africa Games in Johannesburg, Verster established meet records to claim two golds each in the 200 m butterfly (2:04.69) and in the 200 m individual medley (2:04.10).

[16] Verster also sought his entry bid for the 2004 Summer Olympics in Athens, but finished fourth in the 100 m butterfly (54.82) at the South African Championships, handing over to his teammate Eugene Botes.