Jon Jones Says Fiancée Left Him Shortly After Vegas Arrest

Jon Jones is a single man -- the UFC superstar says his fiancée of 9 years, Jessie Moses, has left him for good following his Vegas arrest.

Jones announced the split via Twitter on Wednesday ... saying, "My fiancée left me about two months ago, today she finalized that she won't be coming back."

Worth noting -- the official breakup comes shortly after footage of Jones' September run-in with police was released ... which shows the 34-year-old head-butting a cop car after an alleged altercation with Moses.

"If you are a Jon Jones hater, have a toast, I feel like s***," he added.

Jones and Moses were together for nearly 20 years -- they were high school sweethearts at Union-Endicott High School in New York, split for a short period, and then were engaged in 2013.

Jones and Moses have three kids together -- two 13-year-olds Leah and Carmen and 9-year-old Olivia.

Jones and Moses appeared to make amends after his domestic violence arrest ... posting a video of the then-couple sharing a kiss in the days following the alleged altercation.