William John Bancroft (2 March 1871 - 3 March 1959) was a Welsh international fullback who played club rugby for Swansea and a county cricketer for Glamorgan, becoming their first professional player in 1895.

Bancroft was seen as one of the first true stars of Welsh rugby and played rugby with extreme self-confidence. He possessed great speed and was an excellent kicker of the ball, though some critics felt his defensive play was weak. His brother Jack also played rugby for Wales.