February 5 – The Argentinian president Isabel Perón decrees Operativo Independencia, aiming to neutralize or annihilate the "subversive elements" in the province of Tucuman. Isabelita takes advantage to take a self-coup and assume extraordinary powers.
March 11 – The leftist military government in Portugal defeats a rightist coup attempt involving former president António de Spínola, who flees to Brazil.
March 22 – "Ding-a-dong" by Teach-In (music by Dick Bakker, lyrics by Will Luikinga and Eddy Ouwens) wins the 20th Eurovision Song Contest 1975 (staged in Stockholm) for the Netherlands.
March 31 – Süleyman Demirel of AP forms the new government of Turkey (39th government), a four-party coalition, the so-called First National Front (Turkish: Milliyetçi cephe).
April 5 – The Soviet crewed space mission (Soyuz 18a) ends in failure during its ascent into orbit when a critical malfunction occurs in the second and third stages of the booster rocket during staging at an altitude of 192km, resulting in the cosmonauts and their Soyuz spacecraft having to be ripped free from the vehicle. Both cosmonauts (Vasily Lazarev and Oleg Makarov) survive.
May 6 – The South African government announces that it will provide all Black children with free and compulsory education.
May 15 – Mayaguez incident: The American merchant ship Mayaguez, seized by Cambodian forces, is rescued by the U.S. Navy and Marines; 38 Americans are killed.
The first Cuban forces arrive in Angola to join Soviet personnel who are there to assist the MPLA that controls less than a quarter of Angolan territory. In response, the United States, Zaire and Zambia request South Africa to provide training and support for the FNLA and UNITA forces.[14]
August 1 – The Helsinki Accords, which officially recognize Europe's national borders and respect for human rights, are signed in Finland.
Some members of Jehovah's Witnesses believe that Armageddon will occur this year based on the group's chronology[15] and some sell their houses and businesses to prepare for the new world paradise which they believe will be created when Jesus establishes God's Kingdom on Earth.
August 24 – Officers responsible for the military coup in Greece in 1967 are sentenced to death in Athens. The sentences are later commuted to life imprisonment.
September 15 – The French department of Corse, comprising the entire island of Corsica, is divided into two departments: Haute-Corse (Upper Corsica) and Corse-du-Sud (Southern Corsica).
October 1 – "Thrilla in Manila": Muhammad Ali defeats Joe Frazier in a boxing match in Manila, Philippines. The fight is viewed live by well over 100 million people worldwide.
The South African Defence Force invades Angola during Operation Savannah in support of the FNLA and UNITA prior to the Angolan elections scheduled for November 11.[18]
Tun Mustapha resigns as Chief Minister of Sabah, a state in Malaysia, bringing to an end speculation that he would attempt to lead secession for Sabah to become an independent nation.
November 7 – A vapor cloud explosion at a petroleum cracking facility in Geleen, Netherlands, leaves 14 dead and 109 injured, with fires lasting for five days.[22]
The Treaty of Osimo is signed between Italy and Yugoslavia, resolving their dispute over Trieste. Under the agreement, a majority of the land area and residents go to Italy.[23]
While disabled, the submarine tender USSProteus discharges radioactive coolant water into Apra Harbor, Guam. A Geiger counter at two of the harbor's public beaches shows 100 millirems/hour, 50 times the allowable dose.
December 2 – In Laos, the communist party of the Pathet Lao takes over Vientiane and defeats the Kingdom of Laos, forcing King Sisavang Vatthana to abdicate and creating the Lao People's Democratic Republic. This ends the Laotian Civil War, with mass evacuation of American troops and Laotian civilians, but effectively begins the Insurgency in Laos with the Pathet Lao fighting the Hmong people, Royalist-in-exile and the Right-wings. The Insurgency in Laos wouldn't end until March 30, 2022, when the last unorganized resistance against the Lao People's Army was finally put down.
The Spanish Army quits Spanish Sahara (modern-day Western Sahara), last remnant of the Spanish Empire. The Sahrawi Republic (RASD) is created. Morocco invades the former territory.
Jeffery, Anthea (2009). People's War - New Light on the Struggle for South Africa (1sted.). Johannesburg & Cape Town: Jonathan Ball Publishers. pp.11–12, 14–15. ISBN978-1-86842-357-6.
Osmańczyk, Edmund Jan; Mango, Anthony (2003). "Osimo Treaty, 1975". Encyclopedia of the United Nations and International Agreements: A to F. Taylor & Francis. p.1705.