|Full name||Guillermo Ariel Pereyra|
|Date of birth||20 February 1980|
|Place of birth||Río Cuarto, Argentina|
|Height||1.83 m (6 ft 0 in)|
|Playing position||Defensive midfielder|
|* Senior club appearances and goals counted for the domestic league only.
Born in Río Cuarto, Córdoba, Pereyra began his professional career at Club Atlético River Plate, helping the club to four Primera División titles during his spell there. In January 2004 he was transferred to RCD Mallorca in Spain, eventually becoming an undisputed starter for the La Liga side and making his debut in the competition on 8 February by coming on as a 63rd minute substitute in a 0–3 away loss against Sevilla FC.
In March 2008, Pereyra moved to FC Lokomotiv Moscow, but the Russians decided to terminate the deal shortly after, and he subsequently joined BSC Young Boys on 11 February 2009, initially until the end of the season.
Pereyra returned to Spain in late August 2009, penning a two-year deal with Real Murcia from the second division after arriving on a free transfer. For the following campaign, after the team's relegation, he returned to his country and signed with San Lorenzo de Almagro.
|1999||River Plate||Argentine League Apertura|
|2000||River Plate||Argentine League Clausura|
|2002||River Plate||Argentine League Clausura|
|2003||River Plate||Argentine League Clausura|
- "El Sevilla resuelve en diez minutos" [Sevilla take care of matters in ten minutes]. Mundo Deportivo (in Spanish). 9 February 2004. Retrieved 15 May 2015.
- Профайл игрока – ПЕРЕЙРА Гуиллермо Ариель [Player profile – PEREYRA Guillermo Ariel] (in Russian). Lokomotiv Moscow. March 2008. Archived from the original on 3 July 2009. Retrieved 1 November 2009.
- YB verpflichtet Guillermo Ariel Pereyra (YB acquire Guillermo Ariel Pereyra); Young Boys, 11 February 2009 (German)
- "El argentino Guillermo Pereyra, nuevo jugador del Real Murcia" [Argentine Guillermo Pereyra, new player of Real Murcia]. Marca (in Spanish). 23 August 2009. Retrieved 15 May 2015.
- "San Lorenzo: Pereyra pasó la revisión" [San Lorenzo: Pereyra passed medical] (in Spanish). ESPN Deportes. 15 July 2010. Retrieved 16 July 2010.