| Nguyễn Trung Sơn | |
| Full Name: | Marcos Jeferson Farias Valentim |
| Birth Date: | 29 January 1982 |
| Birth Place: | Brazil |
| Position: | Midfielder |
| Years1: | 2005 |
| Clubs1: | União Rondonópolis |
| Years2: | 2006 |
| Clubs2: | Vila Aurora |
| Years3: | 2007 |
| Clubs3: | SHB Da Nang |
| Years4: | 2008–2009 |
| Clubs4: | Quang Nam FC |
| Years5: | 2011–2013 |
| Clubs5: | Becamex Binh Duong |
| Caps5: | 31 |
| Goals5: | 0 |
| Years6: | 2014 |
| Clubs6: | Quang Nam FC |
| Caps6: | 20 |
| Goals6: | 1 |
| Years7: | 2015 |
| Clubs7: | Dong Thap FC |
| Caps7: | 25 |
| Goals7: | 0 |
Marcos Jeferson Farias Valentim (born 29 January 1982), also known as Nguyễn Trung Sơn, is a Brazilian former footballer who played as a midfielder.
After retiring from professional football, he worked at a hotel in Brazil.[1]
Valentim was born and raised in Brazil, where he had a wife and children.[2] He later became a naturalized Vietnamese citizen[3] and married a Vietnamese woman.[4]