Justin Timberlake was playing golf on July 23 as part of the American Century Celebrity Pro-Am in Lake Tahoe, California, when things took a sudden bad turn.
A fan watching on the sidelines approached the singer-actor as he walked by and seemingly unprovoked, slapped him on the neck -- as seen in video obtained by TMZ.
JT quickly turned around and asked the fan, "Bro, why would you do that?" before moving on through the rest of the crowd.
The slap reportedly did not leave a mark on the superstar.
Security guards for the tournament appeared alarmed by the dustup, but apparently Justin wasn't interested in pressing charges. The Sheriff's Department decided enough was enough, however, and attempted to escort the handsy fan off the golf course grounds.
The fan refused to leave, though, claiming he just wanted to "touch" Justin. According to the Sheriff's Department, the man appeared belligerent and intoxicated, so they promptly arrested him.
Better keep your hands off JT!