May - October 1965
 | July 14 - Mariner 4 flyby of Mars. |
| July 24 - Vietnam War: Four F-4C Phantoms escorting a bombing raid at Kang Chi are the targets of antiaircraft missiles in the first such attack against American planes in the war. One is shot down and the other three sustain damage. |
| July 28 - Vietnam War: US President Lyndon B. Johnson announces his order to increase the number of United States troops in South Vietnam from 75,000 to 125,000. |
| July 29 - Vietnam War: The first 4,000 101st Airborne Division paratroopers arrive in Vietnam, landing at Cam Ranh Bay. |
| July 30 - War on Poverty: US President Lyndon B. Johnson signs the Social Security Act of 1965 into law, establishing Medicare and Medicaid. |
| August 6 - US President Lyndon B. Johnson signs the Voting Rights Act of 1965 into United States law. |
| August 9 - Singapore proclaims its independence from the Malaysian Federation. |
| August 11 - Watts Riots begin in Los Angeles, California |
| August 18 - Vietnam War: Operation Starlite begins as 5,500 United States Marines destroy a Viet Cong stronghold on the Van Tuong peninsula in Quang Ngai Province, in the first major American ground battle of the war. The Marines were tipped-off by a Viet Cong deserter who said that there was an attack planned against the US base at Chu Lai. |
| September 6 - War of 1965: India attacks Pakistan and announces that its forces will capture Lahore (city of Pakistan) in an hour. |
| September 7 - Vietnam War: In a follow-up to August's Operation Starlight, United States Marines and South Vietnamese forces initiate Operation Pirahna on the Batangan Peninsula, 23 miles south of the Chu Lai Marine base. |
| September 14 - Opening of fourth and final period of Second Vatican Council |
| October 15 - Vietnam War: The anti-war student-run National Coordinating Committee to End the War in Vietnam stages the first public burning of a draft card in the United States. |
| October 28 - In St. Louis, Missouri, the 630-foot-tall parabolic steel Gateway Arch is completed. |
| October 30 - Vietnam War: Just miles from Da Nang, United States Marines repel an intense attack by wave after wave of Viet Cong forces, killing 56 guerrillas. Among the dead, a sketch of Marine positions was found on the body of a 13-year-old Vietnamese boy who sold drinks to the Marines the day before. |