- Jan 1 Union of Socialist Soviet Republics established
- Jan 1 Britain's Railways are grouped into the Big Four: LNER, GWR, SR, and LMSR.
- Jan 1 9th Rose Bowl: Southern California beats Penn State, 14-3
- Jan 2 Ku Klux Klan surprise attack on black residential area Rosewood Florida, 8 killed (compensation awarded in 1995)
- Jan 4 1st broadcast of "Barn Dance Show" (WBAP - Fort Worth Texas)
- Jan 7 Baltimore Sun warns of the Ku Klux Klan
- Jan 8 Typography strike in Amsterdam
- Jan 9 Juan de la Cierva makes 1st autogiro flight, Spain
- Jan 9 Swaraj political party founded in India with Chittaranjan Das as president and Motilal Nehru its secretary
- Jan 10 Last US troops leave Rhineland (Germany)
- Jan 10 Lithuania seizes & annexes country of Memel
Agreement of Interest
Jan 19 UK Chancellor of the Exchequer Stanley Baldwin and US Secretary of the Treasury Andrew Mellon agree to reschedule repayment of Britain's $4.5 billion war debt over 62 years
- Jan 23 Taxi strike in Amsterdam begins (through March 9th)
- Jan 24 Aztec Ruins National Monument in New Mexico established
- Jan 25 NVV donates 100,000 guilders to mine workers of Ruhrgebied
- Jan 28 Demonstration against a Dutch University in Ghent
- Jan 29 1st flight of autogiro (Juan de la Cierva, Madrid Spain)
- Jan 31 Montreal Canadiens beat Hamilton Tigers, 5-4 at the Mount Royal Arena, Montreal; first penalty-free game played in NHL history