Ronaldus "Ronald" de Boer (Dutch pronunciation: [roʊ̯.ˈnɑɫ.dʏs ˈroʊ̯.nɑɫt də ˈbur]) (born 15 May 1970 in Hoorn, Netherlands) is a former Dutch football midfielder who has played for the Dutch national team as well as a host of professional clubs in Europe. He is the older twin brother of Frank de Boer.

De Boer's first club was De Zouaven in Lutjebroek where he played before being selected for the Ajax youth programme in 1983. On the professional club level, Ronald played for Ajax (1988–91 and 1993–98), Twente (1991–93), FC Barcelona (1998–2000), Rangers (2000–04), Al-Rayyan (2004–05) and Al-Shamal (2005–08). In both Qatari clubs, he was reunited again with his brother Frank, his teammate at Ajax, Barcelona and Rangers.

While impressive at Ajax during the early 1990s towards the 1998 FIFA World Cup, his high-profile transfer to Barcelona marked what would be an unlikely bad patch for a prolific goal-scoring midfielder as he managed to feature in only 33 games for the club and only scored one goal overall. In the 2000–01 season, he opted to join the Dutch legion at Rangers under the manager Dick Advocaat. Among the Dutch internationals who at that time played for the Rangers were Arthur Numan, Bert Konterman, Fernando Ricksen and Giovanni van Bronckhorst. He spent four seasons with the club before joining Al-Rayyan after the 2003–04 season.