The Miami Heat basketball player proposed to Savannah Brinson, with whom he has two children, at a New Year's Eve party at the SL Nightclub in Miami, according to TMZ.
The couple have been together since they were in high school.
Miami Heat owner Micky Arison tweeted his congratulations to the pair.
"Congrats to Lebron. @KingJames and Savannah so happy 4 u guys (sic)," he wrote.
The athlete celebrated his 27th birthday on December 30.
In August, James was among the top ten least popular celebrities, with a 29% "unfavourable rating".