Most home runs in a Major League Baseball season by a rookie
- Who
- Pete Alonso
- What
- 53 total number
- Where
- United States (New York)
- When
- 29 September 2019
The most home runs in a Major League Baseball season by a rookie is 53, and was achieved by Pete Alonso (USA) playing for the New York Mets, at Citi Field, in Queens, New York, USA, on 29 September 2019.
Pete Alonso aka 'Polar Bear' hit his 53rd home run of the 2019 season against the Atlanta Braves on the penultimate day of the regular season, beating Aaron Judge's mark of 52 home runs by a rookie set in 2017.