The South African Railways Class 91-000 of 1973 was a narrow-gauge diesel–electric locomotive. Between September and December 1973, the South African Railways placed 20 Class 91-000 General Electric type UM6B diesel–electric locomotives in service on its narrow-gauge Avontuur Railway between Port Elizabeth in the Eastern Cape and Avontuur in the Western Cape. Some of them later also worked on the Alfred County Railway out of Port Shepstone in KwaZulu-Natal.