Sicco Leendert Mansholt (Dutch: [ˈsɪkoː ˈleːndərt ˈmɑnsɦɔlt]; 13 September 1908 – 29 June 1995) was a Dutch farmer, politician and diplomat of the Social Democratic Workers' Party (SDAP) and later the Labour Party (PvdA), who served as the fourth president of the European Commission from 1 March 1972 until 5 January 1973.

In 1940, during World War II, he joined the Dutch resistance against the German occupiers and helped shelter refugees.

Following the end of World War II, Mansholt was appointed as acting Mayor of Wieringermeer, serving from 30 April 1945 until 22 May 1945.

After the end of the German occupation, Queen Wilhelmina ordered the formation of a Cabinet of National unity to serve as a caretaker government and make preparations for a new election, and Mansholt was appointed as Minister of Agriculture, Fisheries and Food Supplies in the Cabinet Schermerhorn–Drees, taking office on 25 June 1945.

After the election of 1948 Mansholt returned as a Member of the House of Representatives on 27 July 1948, and continued as Minister in the Cabinet Drees–Van Schaik, taking office on 7 August 1948.

The Mansholt Commission was installed on 1 March 1972 and oversaw the creation of the European Monetary System on 24 April 1972 and the first enlargement on 1 January 1973.

After his retirement, Mansholt occupied numerous seats as a nonprofit director for supervisory boards for several international non-governmental organizations and research institutes (Institute of International Relations Clingendael, European Centre for Development Policy Management, Netherlands Atlantic Association, Transnational Institute, Club of Rome, Humanistic Association, Royal Holland Society of Sciences and Humanities and the Carnegie Foundation) and as an advocate and lobbyist for European integration and humanism.

Mansholt moved to Java in the Dutch East Indies (present-day Indonesia), and started work on a tea plantation.

He helped people who were in acute danger to hide in the Wieringermeerpolder; he organised clandestine food distributions for the western provinces.

In 1954 the parliamentary debate about the budget for the Department of Agriculture was postponed: the Minister was ice-skating the 200-kilometre-long Elfstedentocht in the Dutch province of Friesland, which he skated twice in his life.