Guillermo Gorostiza Paredes (February 15, 1909 - August 23, 1966), known as Gorostiza on the pitch, was a Spanish football forward for Athletic Bilbao from 1929 to 1940. He was born in Santurtzi in Vizcaya.
Signing after playing one season for Arenas and another for Racing de Ferrol, he signed for Athletic and débuted for them on December 1, 1929 in a league match where Athletic beat Real Madrid 2-1. He later went on to score many goals for both Athletic, and also when he moved to Valencia in 1940, staying there until 1946.
After Valencia, he moved to Barakaldo for one season, then retired, but came out of retirement twice to play for Logroñes in 1948-49 and then in 1950-51 for Juvencia Trubia.
He played for the Spanish national side nineteen times, scoring two goals.
Six times Liga de España winner 1929-30, 1930-31, 1933-34, 1935-36, 1941-42, 1943-44.
Five times Copa de España winner 1929-30, 1930-31, 1931-32, 1932-33, 1940-41.
Two times maximum goal-scorer in the Spanish league: 1929-30 and 1931-32.