Simon Alexander Mannering is a New Zealand former professional rugby league footballer who played in the 2000s and 2010s. He played for the New Zealand Warriors in the NRL. A New Zealand international second row forward, who could also play as a centre, he was appointed the New Zealand national team's captain in 2013 and was part of the 2008 World Cup-winning Kiwis team. Mannering was a one-club player who played his whole NRL career with the Warriors. With 301 appearances for the Warriors, Mannering is the club's most capped player.

Mannering moved to Motueka at an early age and was educated at Motueka High School and then at Nelson College from 2000 to 2004, where he played rugby union. After being spotted by rugby league development officer Paul Bergman, Mannering switched codes and was an instant success, making the national secondary schools team after just three games of rugby league.

In 2004 Mannering moved to Wellington to play for the Wellington under-18 side, joining the Wellington Rugby League Academy at WelTec. He then was selected for the Paul Bergman-coached Wellington Orcas in the Bartercard Cup. In 2004, Mannering made the Junior Kiwi's and the New Zealand A side Mannering received interest from the Bulldogs and Parramatta before deciding to move to Auckland and join the New Zealand Warriors.

Mannering made his NRL debut for the Warriors against the Brisbane Broncos in 2005. The match was special as it marked the Warriors' 10th-anniversary match and they upset the then competition leaders for the second time that year. In 2006, Mannering was selected in the New Zealand national rugby league team squad for the 2006 Tri Nations tournament. He played in every game of the series for the Kiwis and was named Rookie of the Year for the Kiwis.

Mannering was selected to play for the New Zealand national team at centre in the 2007 ANZAC Test loss against Australia. Mannering was also one of the nominees for 2007 New Zealand Rugby League Player of the Year. Mannering played all 26 games for the Warriors in 2008 and was named the club's player of the year. In August 2008, Mannering was named in the New Zealand training squad for the 2008 Rugby League World Cup, and in October 2008 he was named in the final 24-man Kiwi squad. In the Kiwis' second match of the tournament, against Papua New Guinea, he scored two tries. He also played in the side that won the final.

In 2009 Mannering signed a new contract with the NZ Warriors club that expired after the 2012 season. He played centre for 20 games in the season for the Warriors to forget. Mannering was appointed the Warriors club captain for the 2010 season. Mannering missed the Kiwis' ANZAC Test match clash with Australia due to injury. Following the 2010 NRL Season, he was selected in the Kiwis' Squad for the 2010 Four Nations tournament and played off the bench in the Four Nations warm-up Test game against Samoa at Auckland's Mount Smart Stadium, which the Kiwis won 50–6.

During the Four Nations, Mannering featured in all of the Kiwis' regular tournament games at Second Row. Following New Zealand's lost to Australia at Eden Park (Round 3 of the tournament), coach Stephen Kearney selected him in the centres for the Grand final against Australia at Brisbane's Suncorp Stadium. New Zealand won the game 16-12 and the 2010 Four Nations tournament.

In 2011, Mannering lead the Warriors to their second Grand Final appearance and he captained the side in the 2011 NRL Grand Final, playing at Second Row against Manly at ANZ Stadium. The Warriors lost the game 24–10. Following the NRL Grand Final, he was selected in the New Zealand Kiwis' Squad for the Newcastle Trans-Tasman Test game against Australia and for the 2011 Four Nations Tournament. In February 2012, Mannering extended his contract once more to see him linked to the club for another three years, with his new contract expiring in 2015. This new contract will see Mannering become one of the New Zealand Warriors' longest serving players, only beaten by Stacey Jones.

In February 2013, Mannering replaced Benji Marshall as New Zealand Kiwis captain. In April 2013, Mannering was originally selected to play New Zealand in the 2013 Anzac Test against Australia, however, only hours before the test game he was ruled out with a calf injury and Kieran Foran took over the captaincy. Following the 2013 NRL Season, he was named in the Kiwis' 2013 Rugby League World Cup Squad. Mannering played in the Kiwis' World Cup warm-up game against the Cook Islands captaining the Kiwis for the first time, playing at second row. The Kiwis went on to win the game 50–0. He played in the Kiwis' first 2013 Rugby League World Cup game against Samoa, playing at lock, and scoring 2 tries in the Kiwis' 42–24 win. The following week, he played in the Kiwis' 48–0 win over France, playing at lock.

Mannering was not a sporting prodigy. He often, perhaps too modestly, describes his early athletic talents as mediocre. But he had an unflagging work ethic towards training and when he came across good mentors he clung to them for dear life. He played 45 Tests for the Kiwis and finished his 14-season playing career with a club record 301 NRL appearances at the end of the 2018 campaign, before the curtain came down on his career. The Simon Mannering Medal, the club's most prestigious award, is presented annually to the New Zealand Warriors player deemed the best performer of the season.

Since retiring Mannering has worked in assistant coaching roles with the Kiwi Ferns in 2018 and the Brisbane Broncos in the WNRL. He has also played a mentoring role at the NZ Warriors.