Alfonso González Nieto (born 2 December 1978 in Madrid, Spain), better known as Fonsi Nieto, is a former Grand Prix motorcycle road racer and the nephew of successful Grand Prix motorcycle road racer Ángel Nieto. After success in the 250cc class he moved to World Superbikes and made one MotoGP start. For 2010 he returned to the Grand Prix scene in the newly formed Moto2 category. Nieto announced his retirement from competition in early 2011 after failing to recover from injuries suffered when racing at Indianapolis in 2010.
He won the Spanish 125cc championship in 1998, and the Spanish 250cc champion in 1999 and 2000, also winning the less prestigious European 125cc title in 1997. In 1999 and 2000 he raced in the 250cc World Championship alongside his domestic commitments, finishing 14th overall on a Yamaha TZ250 with a best result of 6th at Estoril in 2000.
He was 4th in the world championship in 2001, with 4 successive 5th places early in the season and a pair of late-season podium finishes. He won 4 races in 2002, finishing 2nd to Marco Melandri. He was then 5th in 2003 with a win at Donington Park, and 7th in 2004.