Matt Barnes' Fiancee's Ex Sues Over Spitting Incident

The man who Matt Barnes spit on during the 49ers game last weekend is now suing the former NBA champ ... alleging the ex-hooper caused him injury, emotional distress and more during the incident.

David Patterson Jr. -- the ex of Barnes' current fiancee -- filed the lawsuit, obtained by TMZ Sports, in L.A. County Superior Court on Friday.

In the suit, Patterson Jr. claims he had no idea Barnes would be at the much-anticipated Niners vs. Cowboys playoff game in Santa Clara on Sunday ... but said when the two happened to run into each other in a concourse at Levi's Stadium, they began yelling at each other from about 20 feet away.

Patterson Jr. says Barnes then came up to him unprovoked and spat directly in his face. The 37-year-old alleged multiple cell phone cameras captured the incident.

He's suing for battery, assault, and intentional infliction of emotional distress. He's asking for unspecified damages.

Patterson Jr. added in the docs that this was nowhere near the first run-in he's had with his ex-wife's new fiance ... claiming Barnes had harassed him and threatened him repeatedly in the past.

Patterson Jr. says he's got text messages that show the former Golden State Warriors forward called him a "bitch," "clown," "fat f***" and more. He also says at one point in 2022, Barnes told him, "Pull up & get your ass whooped in front of your kids. I'm done talking."

For his part, Barnes said in an application for a temporary restraining order against Patterson Jr. earlier this week that his fiancee's ex was the one who had been harassing him and making threats against him over the past few months.

Barnes also said Patterson Jr. was the aggressor in the altercation at Levi's Stadium.