Francisco Gento won 6 European Cups (now UEFA Champions League) with Real Madrid (1956-1960, 1966), which was the record for most titles by a single player when this question was written. He was part of Real Madrid's legendary team that won 5 consecutive European Cups. However, claims about 'most title-winning side' can vary by competition and era. Players like Paolo Maldini (5 Champions League titles) and others have also won multiple titles.