Here comes the … ex?

A wedding turned into a nightmare when the groom’s ex-girlfriend attended his nuptials at his invitation — and the bride later accused her of being out to steal her husband.

The 36-year-old woman, who herself is married, recalled on Reddit that the two “amicably split up” after dating from ages 15 to 18 simply because they opted to go to faraway colleges.

“Since college, we’ve kept in ‘Facebook familiar’ contact, where we’d wish each other happy birthday, or congratulate each other on big milestones, but have had no other contact in the 20 or so years since then,” the ex-wrote.

“About a year ago, I saw his engagement post on his Facebook and congratulated him.”

A few months after that, the 37-year-old now-married man messaged her to catch up on life since the glory days of high school and additionally expressed interest in a hometown wedding reunion with her and some more mutual friends.

She accepted the invitation.

Fast forward to the ceremony, she said things were “incredibly normal,” and the old gang from high school all “had a great time.”

Things went south quickly, though.

“Sunday morning I wake up to a slew of Facebook messages from my ex’s new wife about my audacity to attend the wedding and how out of all his former girlfriends, I was the only one who failed the test,” the woman wrote.

“She said that CLEARLY you shouldn’t attend an ex’s wedding unless you’re still hung up on them and how I must be planning to steal her new husband away.”

The woman first apologized and stated she simply went to reunite with old friends, but the bride wasn’t buying it.

“She immediately responded and again said that no sane woman, with good intentions, would ever think it was okay to attend their ex’s wedding.”

Still apologetic, she then messaged her ex to say that she had no ulterior motives for attending. The man then said that the invitation had been “sincere” and he apologized for his new wife going off the rails.

“I left it at that, thinking it was a closed matter. A few hours later the new wife is messaging me again, complaining about how I was trying to manipulate her new husband to make her look crazy.”

She then sent screenshots to her ex and decided it was best to block them both to avoid any more unwanted dramatics.

Still, hell hath no fury like an angry bride.

“Yesterday I started getting messages from the [bride’s] sister saying I poisoned my ex against his new wife and I should have kept the messages to myself,” the woman added.

“[I’m] also being told I could have just avoided all of this by knowing I [shouldn’t] attend my ex’s wedding.”

Asking the online community if she was in the wrong for attending, the woman was met with a resounding not guilty verdict.

“Wow, that’s bat crap crazy. So you went to the wedding with your husband and he’s your wingman while you try to rekindle your high school relationship … with the groom … on his wedding day?!” one said of the bride’s thought process.

Meanwhile, another said this is a huge, belated red flag for the newlywed man.

“Hopefully it’s not too late for him to get an annulment … his bride sounds … well, psychotic.”