Mark Bradley Geyer OAM (/ɡaɪər/) (born 7 December 1967) is an Australian radio host and former professional rugby league footballer who played in the 1980s, 1990s and 2000. An Australian international and New South Wales State of Origin representative second-rower, he is a rugby league media identity. Geyer's club career was played primarily with Penrith, with whom he won a premiership in 1991, as well as the Balmain Tigers and the Western Reds. He is the brother of fellow former professional rugby league footballer Matt Geyer and the father of current Penrith Panthers player Mavrik Geyer.

Geyer was part of the Triple M on-air team for the Sydney breakfast show called The Grill Team from 2009 to 2017 before moving to an evening slot—The Rush Hour—on the same station.

In 1987, Geyer established a regular first-grade place with the Penrith Panthers and was selected for the City Seconds team after only a handful of top-grade appearances. He also played in Penrith's 1987 Reserve Grade Grand Final winning team that defeated the Manly-Warringah Sea Eagles 11–0 at the Sydney Cricket Ground.

Geyer was first selected in the second row for New South Wales in game 3 of the 1989 State of Origin series, at Lang Park in Brisbane.

His 1990 season was largely lost to a succession of injuries ^{[citation needed]} that restricted him to just 12 games, though he did play in Penrith's maiden Grand Final appearance (an 18–14 loss to the Canberra Raiders) and from there was selected, along with Panthers teammates Greg Alexander, John Cartwright and Brad Fittler, for the 1990 Kangaroo tour. Geyer played in 11 games on the Kangaroo Tour, scoring four tries and earning his first Australian test jumper when he was selected on the bench for the first test against France at the Parc de Sports in Avignon.

Geyer's form for the Panthers in 1991 again earned him selection for NSW during the State of Origin series. Geyer received a five-match suspension for an incident in the second game at a wet Sydney Football Stadium, which was preceded by a half-time confrontation with Queensland captain Wally Lewis in which referee David Manson and NSW captain Ben Elias had to stand between the two, who twice almost came to blows. He was cited for an elbow to the head of Queensland fullback Paul Hauff, which sparked an all-in brawl. His suspension saw him unavailable for selection in the first test of the 1991 Trans-Tasman Test series against New Zealand in Melbourne, though after the Australians lost the test 24-8 a number of changes were made and Geyer's form was rewarded with selection in the second test in Sydney and the third in Brisbane. The Aussies went on to win the final two tests to wrap up the series 2–1.

In August 1991, he was thought to be out for the rest of the season after injuring his ankle ligaments in a training session, only to return for the major semifinal. However, despite his problems during the season, Geyer helped the minor premiers into the Grand Final where they gained revenge on Canberra with a 19–12 win that saw the Panthers win their first premiership since entering the competition in 1967. Geyer had a hand in all three of the Panthers tries on the day and was judged to be their best player, though his sin-binning for dissent by referee Bill Harrigan during the second half was thought to have cost him the Clive Churchill Medal as man of the match.

He spent the 1993 season with the Balmain Tigers. After leaving Penrith, the coach of Balmain at the time Alan Jones handed Geyer a lifeline. Speaking to the media in 2018 Geyer spoke of his time at Balmain saying "It was shit to be honest, I didn't like it one bit, I didn't like travelling on the M4, which at the time only had two lanes all the way to Leichhardt Oval in peak hour then driving home in peak hour, take all that aside from it, the people involved with the Tigers at the time I loved. Alan Jones was the only coach in Sydney who would throw me a lifeline after I left Penrith in controversial circumstances".