is a Chilean former professional footballer who last played as a midfielder for Chilean Primera División club Universidad de Chile. He is usually deployed as a central midfielder, although he can also operate in a holding role in front of the back-line, in a more attacking position in the hole behind the strikers, or even as a deep-lying playmaker. An intelligent and technically gifted player, who possesses significant physical strength in spite of his diminutive stature, and an ability to dictate play in midfield, Pizarro is known in particular for his vision, range of passing, dribbling skills, and ability from set pieces.

Pizarro began his career in Chile with Santiago Wanderers, and later also played for Universidad de Chile in his home country; he later had spells with several Italian clubs, and also briefly played on loan with English side Manchester City in 2012, before returning to Chile in 2015. During his stay in Italian football, he won one Serie A title (2005–06), three Coppa Italia titles and two Supercoppa Italiana titles, while playing for Inter Milan and Roma; he also played for Udinese and Fiorentina during his time in Italy. His Italian nickname is \"Pek\", diminutive of \"pequeño\", meaning \"small\" in Spanish, because of his short stature (1.68 metres).

Pizarro played for the Chile national team, with which he won the bronze medal at 2000 Summer Olympics, and played at two Copa América tournaments. He made his full debut in 1999, playing at that year's Copa América, and was part of the Chilean squad which won its first-ever tournament in 2015.

In November 2018, he announced his retirement from professional football. His last match was on 2 December 2018, as a captain of Universidad de Chile, against Curicó Unido.