Kieran Paul Sadlier (born 14 September 1994) is an English-born Irish footballer who plays as a midfielder for League One club Doncaster Rovers. Sadlier previously won both the League of Ireland Premier Division and FAI Cup in his first season with Cork City.
A youth team player with Cambridge United, Sadlier joined West Ham United in 2005. After finishing top goal scorer for the U18s in their 2012–13 season, Sadlier went on to feature regularly for the U21s, he requested to be released from his contract early in January 2015 in order to sign for St Mirren until the end of the 2014–15 season.
Sadlier made his debut on 28 February in a 1–0 home win against Hamilton Academical coming on as a half-time substitute for Viktor Genev. He made his full home debut against Celtic on 3 April 2015 in a Good Friday evening televised game that Celtic went on to win 0–2.v Sadlier scored his only goal for St Mirren in a 4–1 home victory against Kilmarnock on 25 April 2015.