Sergio Daniel Martínez Alzuri (born 15 February 1969), nicknamed "Manteca", is a Uruguayan former professional footballer who played as a striker. He was two times top scorer in the Argentine Primera División during his five years with Boca Juniors. He also played professionally in Spain.
In his five years with Boca, Martínez won the Apertura in 1992 and the Copa de Oro in 1993, being crowned the Apertura 1993's top scorer with 12 goals and the Clausura 1997's with 15; upon his departure, he ranked seventh in the club's all-time scoring list with 86 goals in 167 games (all competitions).