Alberto Agustín Castillo Gallardo (born May 5, 1963) is a former Peruvian professional footballer and currently manager.

He started his career with Alianza Lima in 1973. He was part of the squad that won the 1975 tournament. He played in the Peruvian Segunda División until 1978, when he moved to Club Atlético Chalaco.

In 1989, he traveled to Ecuador to play with Deportivo Cuenca.

In 1990, Castillo joined Atlético Marte of El Salvador, he then moved to Costa Rica to play with Herediano.

In 1994, he returned to El Salvador to play with Águila.

In 1996, he signed with FAS, where he retired.

In 1997, he began his coaching career with Deportivo Municipal in his native country of Peru.

In August 2000, Castillo signed as new coach of Municipal Limeño of El Salvador, replacing Rubén Alonso.

Castillo led them to the Apertura 2000 final, but they were defeated by Águila (2–3).

Most of his success was when he became the manager of FAS in July 2001, replacing Rubén Guevara. Castillo led them to win the Clausura 2002, Apertura 2002, Apertura 2003, Apertura 2004 and Clausura 2005. Also, FAS lost the Clausura 2004 final against Alianza on penalties.

In October 2005, Castillo was replaced by Carlos de los Cobos.

In September 2005, Castillo signed as new coach of Chalatenango, replacing Carlos Alberto Mijangos. Castillo was replaced by Vladan Vićević in 2007.

In December 2007, he signed as coach of Águila, replacing Luis Ramírez Zapata. In December 2008, Castillo was replaced by Pablo Centrone.

In December 2008, he signed as coach of Luis Ángel Firpo, replacing Óscar Emigdio Benítez. Castillo led them to the Clausura 2009 final, but they were defeated by Isidro Metapán (0–1).

In December 2009, Castillo was replaced by Hugo Coria.

He then accepted to coach Suchitepéquez of Guatemala, and helped the small club reach the semi-finals of the Clausura 2010.

In January 2011, Castillo signed again as coach FAS, replacing Jorge Abrego. Castillo led them to the Clausura 2011 final, which they lost against Alianza (1–2 defeat). At the end of the tournament, he returned to Peru to coach Sport Boys.

On December 17, 2012, he was announced as new manager to El Salvador, replacing Juan de Dios Castillo. On December 20, 2013, he was sacked as manager of El Salvador.

In September 2014, Castillo signed as coach of FAS, replacing Efraín Burgos. Castillo led them to the Apertura 2015 final, but they were defeated by Alianza (0–1 defeat). In December 2015, Castillo was replaced by Carlos "Ché" Martínez.

In May 2016, Castillo signed as new coach of Sonsonate for the Apertura 2016, replacing Ennio Mendoza and Mario Elias Guevara. Castillo led them to the semi-finals of that tournament, but they were defeated by Alianza 0–4 on aggregate.

He left the club in February 2017.

In December 2017, Castillo signed again as coach of Suchitepéquez.

In March 2018, Castillo signed as new coach of Isidro Metapán, replacing Edwin Portillo. In December 2018, Isidro Metapán reached the quarter-finals of the Apertura 2018, but they were defeated by FAS 0–2 on aggregate. On 12 December 2018, Castillo left the club.

C.D. Municipal Limeño

• Primera División
  • Runners-up: Apertura 2000

C.D. FAS

• Primera División
  • Champion: Clausura 2002, Apertura 2002, Apertura 2003, Apertura 2004, Clausura 2005
  • Runners-up: Clausura 2004, Clausura 2011, Apertura 2015

C.D. Luis Ángel Firpo

• Primera División
  • Runners-up: Clausura 2009

• Agustín Castillo at Soccerway (in Spanish)