Simon Paul Poidevin (born 31 October 1958) is a former Australian rugby union player who played as a flanker. Poidevin made his Test debut for Australia against Fiji during the 1980 tour of Fiji. He was a member of the Wallabies side that defeated New Zealand 2–1 in the 1980 Bledisloe Cup series. He toured with the Eighth Wallabies for the 1984 Australia rugby union tour of Britain and Ireland that won rugby union's "grand slam", the first Australian side to defeat all four home nations, England, Ireland, Wales and Scotland, on a tour. He made his captaincy debut for the Wallabies in a two-Test series against Argentina in 1986, substituting for the absent Andrew Slack. He was a member of the Wallabies on the 1986 Australia rugby union tour of New Zealand that beat the All Blacks, one of six international teams and second Australian team to win a Test series in New Zealand. During the 1987 Rugby World Cup, he overtook Peter Johnson as Australia's most capped Test player against Japan, captaining the Wallabies for the third time in his 43rd cap. He captained the Wallabies on a fourth and final occasion on the 1987 Australia rugby union tour of Argentina before injury ended his tour prematurely. In 1988, he briefly retired from international rugby, reversing his decision 42 days later ahead of the 1988 Bledisloe Cup series. Following this series, Poidevin returned to the Australian side for the single 1989 Bledisloe Cup Test. He returned full-time to the Australian national squad for the 1991 season. Poidevin was a member of the Wallabies that won the 1991 Rugby World Cup, after which he retired from international rugby union.

Poidevin is one of only four Australian rugby union players, along with David Campese, Michael Lynagh and Nick Farr-Jones, to have won rugby union's Grand Slam, achieved a series victory in New Zealand, and won a Rugby World Cup.

Poidevin married Robin Fahlstom in 1995 and they have three sons.^{[citation needed]}

Simon Paul Poidevin was born on 31 October 1958 to Ann (née Hannan) and Paul Poidevin at Goulburn Base Hospital in Goulburn, New South Wales. He is the third of five children. His two older siblings are named Andrew and Jane, and his two younger siblings are called Joanne and Lucy. Poidevin's surname comes from Pierre Le Poidevin, a French sailor who was imprisoned by the English in the 1820s, but eventually settled in Australia and married an Irish woman. Poidevin was raised on a farm titled "Braemar", which is a 360-hectare property located on Mummell Road just outside of Goulburn, New South Wales, on which his family raised fat lambs and cattle.

Poidevin's family has a history containing many sporting achievements. His grandfather on his mother's side of his family, Les Hannan, was a rugby union player and obtained selection for the 1908–09 Australia rugby union tour of Britain. However, he broke his leg before the team departed from Australia and missed the tour. Hannan later fought in World War I in the 1st Light Horse Brigade, where he served as a stretcher bearer.

Poidevin's father's cousin, Dr Leslie Oswald Poidevin, was an accomplished cricketer, hitting 151 for New South Wales against McLaren's MCC side, and during the 1918–19 season he became the first Australian to score a century at all levels of cricket. He later became co-founder of the inter-club cricket competition in Sydney known as the Poidevin-Gray Shield. Dr Lesile Oswald Poidevin was also an accomplished tennis player. While studying medicine in Great Britain, he won the Swiss tennis championship and also played in the Davis Cup. In 1906, he represented Australasia with New Zealander, Anthony Wilding, when they were beaten by the United States at Newport, Wales. After this loss, Poidevin traveled to Lancashire to play cricket, where he made a century for his county the following day. Dr Leslie Oswald Poidevin's son, Dr Leslie Poidevin, was also an accomplished tennis player who won the singles tennis championship at Sydney University six years in a row between 1932 and 1937.

Poidevin's eldest sibling, Andrew, obtained a scholarship to study at Chevalier College at Bowral, where he represented NSW schoolboys playing rugby union. He went on to play rugby union for the Australian National University, ACT U-23s at breakaway, and later played with Simon for the University of New South Wales.

Poidevin's first school was the Our Lady of Mercy preparatory school in Goulburn where he was introduced to rugby league. He played for an under-6 team that was coached by Jeff Feeney, the father of the well-known motorbike rider, Paul Feeney. For his primary education, Poidevin attended St Patrick's College (now Trinity Catholic College), where rugby league was the only football code. His first team at St Patrick's College was the under-10s. During his childhood, Poidevin played rugby league with Gavin Miller, who would go on to play rugby league for the Australia national rugby league team, New South Wales rugby league team and Cronulla-Sutherland Sharks.