James Theunissen (born 7 December 1981) was an English cricketer.
He was a right-handed batsman and a right-arm medium-fast bowler who played for Berkshire.
He was born in London and educated at Douai School.
Theunissen represented Berkshire in the Minor Counties Championship for three seasons, and made a single List A appearance for the team, in the 2003 C&G Trophy, against Durham.
Batting at number 11, Theunissen scored 16 runs, assisting fellow tailender Tom Lambert to a match-best tenth-wicket partnership of 30 runs.
Theunissen continued to represent Berkshire in the Minor Counties Championship until 2004.
In the 2006 Cockspur Cup, he played for North Maidenhead and Falkland.