Rennie began refereeing in 1979 in local leagues, then operated in the Northern Premier League until 1994, at which time he was appointed to the Football League List of referees. He was given his first Premiership appointment on 23 August 1997, a game between Leeds United and Crystal Palace at Elland Road.^[3] Rennie became a FIFA referee in 2000,^[4] and joined the Select Group of professional referees the following year. Keith Hackett, head of the Professional Game Match Officials Board has described him as "the fittest referee we have ever seen on the national and world scene."^[5] At the end of 2004, he retired from the FIFA list, after reaching the compulsory age of 45 but made a return to active refereeing in November 2007.^[6] In September 2010, Rennie became president of Hallam FC which was celebrating its 150th anniversary season.

Rennie was born in Sheffield, where he still lives. He practises both kick-boxing and aikido, and has a master's degree in business administration and law. He is also a magistrate in Sheffield.^[7] He is married and has one daughter and a son.^[5] He appeared as himself in the BBC Two drama Marvellous, broadcast in September 2014.^[8]

In August 2015, he became the referee in the ITV game show, Freeze Out, presented by Mark Durden-Smith.^{[citation needed]}

In November 2023, he was awarded an honorary doctorate at Sheffield Hallam University for his work in the community of Sheffield, namely Sheffield Federation for School Sports and Weston Park Hospital.^{[citation needed]}

• Uriah Rennie Referee Statistics at soccerbase.com