Stephen Charles Mortimer, also nicknamed "Turvey", is an Australian former rugby league footballer who played as a halfback. Mortimer played a Canterbury-Bankstown Bulldogs club record 272 first-grade games between 1976 and 1988, winning four premierships with the club during the 1980s. Mortimer's two younger brothers, Peter and Chris, also played for the club.

Mortimer was born in the Sydney suburb of Yagoona and raised in Wagga Wagga, New South Wales, the eldest son of Ian and Elaine Mortimer's four sons. His brothers (Peter, Chris, and Glen) also played rugby league and were famously known as the Mortimer brothers. Spotted by Peter "The Bullfrog" Moore, when playing for Riverina in the 1975 Amco Cup, Mortimer tore his future club Canterbury-Bankstown Bulldogs to pieces and was Man of the Match despite Riverina losing. 'Bullfrog', when asked about Mortimer's performance uttered the words "will never play against Canterbury-Bankstown ever again", and true to Bullfrog's word he never did. Mortimer captained Canterbury to Premierships in 1984 and 1985 and was a member of the 1980 and 1988 triumphs.

His performances in the 1980 and 1985 victories were vintage Mortimer. In the 1980 decider, he saved three certain Eastern Suburbs tries through superb cover tackles (a great Mortimer trademark). In the 1985 Grand Final it was Mortimer's captaincy and direction that controlled Canterbury field position and possession as they buried St George into submission following a try to brother Peter Mortimer in the 29th minute. Mortimer captained Canterbury to a narrow loss in the 1986 Grand Final, which Parramatta won 4–2 in a tryless game, and also played in the 1979 Grand Final loss to St George.

During Mortimer's final five seasons at Canterbury-Bankstown, he formed a great halves combination with the master of support play in Terry Lamb. During their five years together in the blue and white, the Bulldogs made four Grand Finals and won three of them. Lamb was a non-playing reserve in the 1985 Grand Final win over St George after being ruled out due to injury, and Mortimer missed 68 minutes of the 1988 Grand Final win over Balmain in the first Grand Final played at the Sydney Football Stadium (Turvey had broken his arm during the Bulldogs Round 21 match against St George at Belmore, but recovered sufficiently to take his place in Phil Gould's side on GF day).

Lamb would later captain the Bulldogs between 1990 and 1995 and usher in a new breed of Bulldogs that weren't around in the Mortimer era. Mortimer received an offer to switch clubs in 1987 and very nearly joined the Bob Fulton coached Manly-Warringah Sea Eagles, but stayed put at Canterbury (Manly won the premiership that year while the Bulldogs finished only 1 point out of the finals). He was advised to retire after 1988 rather than join another club, which ensured his status as one of the most loyal players to play the game of rugby league.

Surprisingly, despite their success when playing together at Canterbury, Mortimer and Lamb only ever partnered each other once in the halves for New South Wales. This was in Game 2 of the 1984 State of Origin series on a very wet and muddy Sydney Cricket Ground (SCG), with Queensland winning 14–2. They never got the chance to play together for Australia as Queensland captain Wally Lewis was the test five-eighth and also test captain from 1984.

Despite troubles at Canterbury during his latter years, including a well publicised feud with Warren Ryan who coached the team from 1984 to 1987, Mortimer was a one-club man and retired playing 272 first grade games, which at the time was the most for one NSWRL club.

Mortimer's representative career faced challenges from other great halfbacks of his era including Tommy Raudonikis, Steve Morris, Kevin Hastings and most notably, Peter Sterling.

Despite the presence of great halfbacks, Mortimer played 16 matches for New South Wales between 1977 and 1985, including nine under the State of Origin banner. Mortimer captained the Blues in 1984/85 in three matches (all victories) and was the first captain to lead New South Wales to State of Origin success in 1985. He was also named man-of-the-match in the final game of the 1984 State of Origin series at Brisbane's Lang Park. Mortimer is credited as the player who finally brought passion into the Blues Origin jersey and led a new wave of NSW players that would be the core of the team for many years to come including those such as Wayne Pearce, Brett Kenny, Michael O'Connor, Garry Jack, Royce Simmons, Steve Roach, Noel "Crusher" Cleal, Ben Elias, and his brother Chris Mortimer.

Mortimer played 8 Test matches for Australia between 1981 and 1984 where he scored two tries in his Test debut against France at the SCG with Australia winning 43–2. Also making his debut in that Test match was future rugby league immortal Wally Lewis, who played outside Mortimer at five-eighth.

Steve Mortimer's final year at Canterbury was under the coaching of Phil Gould where he stood down from the captaincy after Round 5. Mortimer's performances on the field were vintage but a virus and broken wrist cut his appearances to just 14 and also played 5 games as a fresh replacement. The NSWRL allowed teams for the first time outside of semi-finals to have fresh reserves for club matches and Gould utilised Mortimer when he returned from a virus to great effect including one match and his only time against Allan Langer where in 31 minutes Mortimer turned a club match against the  Brisbane Broncos on its head to win Man of the Match.

The Bulldogs' salary cap crisis in 2002 saw Mortimer return to the club to save them from trouble. He led from the front with the passion and dedication he displayed on the field. The Bulldogs emerged from the dramas with flying colours for the 2003 season. They fell one game short of the Grand Final but the signs were there for a big 2004. Further dramas in the pre-season saw Mortimer stand down as chief executive officer but the foundations he put in place and the players he helped recruit saw Canterbury under the coaching of Steve Folkes win their 8th Premiership.

Steve Mortimer will be remembered as one of the all-time great halfbacks, a player who brought the passion into the State of Origin for New South Wales, a great captain for his state and country and a great ambassador for the sport of rugby league on and off the field. In 1988, Mortimer was awarded the Order of Australia Medal (OAM) for his services to rugby league. On 24 October 2000, Mortimer was recipient of the Australian Sports Medal. In February 2008, Mortimer was named in the list of Australia's 100 Greatest Players (1908–2007) by the NRL and ARL to celebrate the code's centenary year in Australia.