Event of Interest
May 2 Eugene O'Neill's "Moon for the Misbegotten" premieres in NYC

Eugene O'Neill
- May 3 73rd Kentucky Derby: Eric Guerin aboard Jet Pilot wins in 2:06.8

Douglas MacArthur
- May 7 Paraguayian government unleashes contra revolt
Event of Interest
May 8 A movement among Card players to protest its 1st meeting with Jackie Robinson & the Dodgers is aborted by a talk from owner Sam Breadon

Jackie Robinson
Event of Interest
May 8 Polish resistance fighter Witold Pilecki, who had volunteered to be imprisoned in Auschwitz to gain information about the Holocaust, is arrested by Polish communist police

Witold Pilecki
- May 10 "Chocolate Soldier" closes at Century Theater NYC after 69 performances
- May 10 72nd Preakness: Doug Dodson aboard Faultless wins in 1:59
- May 11 BF Goodrich announced the development of tubeless tire (Akron Ohio)
- May 11 Laos accepts constitution for parliamentary democracy
- May 13 US Senate approved the Taft-Hartley Act limiting the power of unions
Event of Interest
May 16 Billie Holiday is arrested in her New York apartment for possession of narcotics

Billie Holiday
- May 17 "Street Scene" closes at Adelphi Theater NYC after 148 performances
- May 18 A's catcher Warren Rosar catches his 147th game without an error
- May 22 "Truman Doctrine" goes into effect, aiding Turkey and Greece
- May 22 1st US ballistic missile fired
- May 23 PC Hooft prize forms for literature
- May 25 Coal dust explosion rocks Centralia Coal Co's Mine #5 killing 111
- May 30 Indianapolis 500: Mauri Rose wins in 4:17:52.159 (187.228 km/h)
- May 31 79th Belmont: Ruperto Donoso aboard Phalanx wins in 2:29.6
- May 31 Communists seize power in Hungary
- May 31 Eastern DC-4 crashes between Ft Deposit & Perryville Md, kills 53
- May 31 Italian government of Gasperi forms