The world's first space nuclear power reactor, SNAP-10A, is launched by the United States from Vandenberg AFB, California. The reactor operates for 43 days and remains in Low Earth orbit.
The first jet-to-jet combat of the Vietnam War occurs. Although all American aircraft involved return safely, the North Vietnamese Air Force claims to have shot down a U.S. Navy F-8 Crusader fighter and in future years celebrates April 3 as "North Vietnamese Air Force Day."
Irish general election, 1965: A general election takes place in Ireland, the first Irish General Election to be covered on television by state broadcaster RTÉ. The ruling Fianna Fáil party obtains an additional two seats in the election, giving it an overall majority in the Dáil.
Soviet spacecraft Luna E-6 No.8, intended to be the first spacecraft to perform a soft landing on the Moon, is lost in a launch failure when a nitrogen pipeline in the oxidiser tank depressurises, causing a loss of oxidiser flow to the engine and resulting in the engine cutting off. The spacecraft fails to achieve orbit, and disintegrates on re-entry.
Indonesia–Malaysia Confrontation: Lieutenant-Colonel John Williams, serving as a Company Sergeant Major with the 2nd Battalion, The Parachute Regiment, wins the DCM for gallantry for his role in defending the base at Plaman Mapu; Williams loses an eye in the battle and thereafter gains the nickname "Patch".
Vietnam War: Prime Minister of Australia Robert Menzies announces that the country will substantially increase its number of troops in South Vietnam, supposedly at the request of the Saigon government (it is later revealed that Menzies had asked the leadership in Saigon to send the request at the behest of the Americans).
^Palmer, Alan; Veronica (1992). The Chronology of British History. London: Century Ltd. pp. 423–424. ISBN0-7126-5616-2.
^Walter Lucas, "Western liaison—'Bilderberg' style", Christian Science Monitor, April 12, 1965, p. 11.
^Nichols, CDR John B., and Barret Tillman, On Yankee Station: The Naval Air War Over Vietnam, Annapolis, Maryland: United States Naval Institute, 1987, ISBN 978-0-87021-559-9, p. 152, which also claims this event occurred on April 3.
^Polmar, Norman, "Historic Aircraft: The Last Photo Plane", Naval History, October 2010, p. 64.
^"Helicopters Save 41 Shipwrecked Men" The Times (London). Tuesday, 6 April 1965. (56289), col B, p. 9.
^Taylor, John W R. (editor). Jane's All the Worlds Aircraft 1988-89. Coulsdon, Surrey, UK: Jane's Information Group, 1988. ISBN 0-7106-0867-5. p7
^Theodore Shabad, "Moscow Puts Aloft Its First 'Comsat'; TV Movie Is Shown", New York Times, April 24, 1965, p. 1. "According to a Moscow television spokesman the unannounced direct telecast from Vladivostok, which included a documentary film of the life of Pacific fishermen, began at 9 A.M. Moscow time (4 P.M. Vladivostok time) and lasted about three hours. Since no television programs are scheduled in Moscow before noon, virtually no home television viewer had turned on his set and watched the live transmission. A two-minute recorded excerpt was repeated during news periods later in the day."
^"Sukarno Seizes Foreign Firms", Los Angeles Times (AP), April 25, 1965, p. 10.
^Los Angeles Times, April 27, 1965 "Highway Sniper's Bullet Proves Fatal to Boy, 5"