William Boyd Rankin (born 5 July 1984) is an Irish cricketer who has played international cricket for both England and Ireland. He is a right-arm medium-fast bowler. He is the brother of David Andrew Rankin. Rankin is a tall bowler who stands at 6 ft 8 inches and has a distinctive bouncing action in his bowling. Rankin revealed in an interview that his action is modelled on bowlers like Curtly Ambrose and Glenn McGrath who "hit the deck from just back of a length outside off stump". He studied agriculture at Harper Adams University College in Shropshire, during which time he worked on his batting technique.

In August 2012, Rankin announced that he would cease playing for Ireland, with the hope of one day playing for the English team. He debuted for England against New Zealand in a T20 match on 25 June 2013, and later played one Test for England during the 2013-14 Ashes series in Australia.

With few prospects of a return to the England team, Rankin confirmed in December 2015 that he would commit to playing for Ireland in the upcoming 2016 ICC World Twenty20. He has subsequently represented Ireland in both 20 and 50-over formats. He was one of the eleven cricketers to play in Ireland's first ever Test match, against Pakistan, in May 2018.