| Zainuddin Kassim | |
| Fullname: | Haji Zainuddin bin Haji Kassim |
| Birth Date: | 1 November 1965[1] |
| Birth Place: | Brunei |
| Position: | Striker |
| Clubs1: | Brunei |
| Nationalteam1: | Brunei |
| Nationalcaps1: | ? |
| Nationalgoals1: | 3+ |
| Manageryears1: | 1988 |
| Managerclubs1: | Brunei (player-coach) |
| Manageryears2: | 2001 |
| Managerclubs2: | Brunei |
| Manageryears3: | 2004 |
| Managerclubs3: | Brunei |
| Manageryears4: | 2008–2011 |
| Managerclubs4: | AM Gunners |
| Manageryears5: | 2011 |
| Managerclubs5: | Brunei U19 |
| Manageryears6: | 2013 |
| Managerclubs6: | Brunei U23 (assistant coach) |
| Manageryears7: | 2020 |
| Managerclubs7: | Brunei (assistant coach) |
| Pcupdate: | 25 August 2015 |
| Ntupdate: | 25 August 2015 |
Haji Zainuddin bin Haji Kassim is a Bruneian former national football player and current coach.
Zainuddin played as a striker for the Bruneian representative team in the Malaysia league in the 80s and 90s.[2] He made several appearances for the national side, and scored a goal in a 1986 World Cup qualifier against Hong Kong.
Zainuddin became a football coach afterwards. After a coaching stint for Brunei's M-League side while still registered as a player in 1988,[3] he took charge of the national team for 6 games at the 2002 World Cup qualifying.[4] He then turned to club football in 2008 with AM Gunners,[5] coaching them until 2011 when the season was aborted abruptly. He was appointed Brunei Under-19 head coach in 2011,[6] followed by being Brunei Under-23 assistant coach in 2013.[7]
In 2020, he was appointed assistant coach of the Brunei national football team headed by Ali Hj Mustafa.[8]