Per Bengt Magnus Ingemar Rösiö (14 May 1927 – 19 May 2019) was a Swedish diplomat and author. He was Ambassador to 17 countries and wrote 20 books, mainly on diplomacy. He was known however for having conducted the Swedish government's inquiry into the death of the UN Secretary General Dag Hammarskjöld where he said that there was no foul play.
Rösiö was administrative director of the Dag Hammarskjöld Foundation from 1962 to 1964, first embassy secretary in Washington, D.C. from 1964 to 1965, United Nations Deputy Resident Representative in Algiers in 1965 and embassy counsellor in Khartoum from 1966 to 1969. He was consul general in Houston from 1969 to 1971 and deputy director at the Foreign Ministry from 1972 to 1973.