Jan Herman van Roijen (10 April 1905, Constantinopel – 16 March 1991, Wassenaar) was a Dutch diplomat and politician. He was Dutch foreign minister in 1946.
Van Roijen was the son of Jan Herman van Roijen Sr (1871–1933) and the American Albertina Taylor Winthrop (1871–1934). When Jr was born, his father was a diplomat in Constantinople.
The diplomatic career of van Roijen began in the 1930s when he held positions in embassies in Washington and Tokyo as well as positions at the Ministry of Foreign Affairs in the Hague. Following the war, he represented the Netherlands at various conferences linked to the nascent United Nations, including the United Nations Conference on International Organization in San Francisco. After his brief stint as the Dutch foreign minister he was the ambassador to Canada (1947–1950), to the United States (1950–1964) and jointly to the United Kingdom and to Iceland (1964–1970).
In 1982 he received the inaugural Freedom of Fear Award and in 1984 he received the Wateler Peace Prize for his diplomatic efforts.