According to legal docs, obtained by TMZ, Dolan is named as a defendant in a suit alleging he partook in outright sex trafficking after taking a young masseuse under his wing between late 2013 and early 2014 ... while he was performing on the road.

The plaintiff, Kellye Croft, claims she was initially hired to be the traveling massage therapist for the Eagles in 2013 ... but after some trouble with the touring staff, she says she ended up meeting Dolan, whose own band was the opening act.

Croft says she opened up to JD about her woes, and afterward, he apparently got involved to alleviate her issues ... and, she alleges he started pushing a sexual relationship with her.

While she doesn't straight up accuse Dolan of sexual assault, Croft does say she felt pressured to engage in sex acts with him ... throughout the rest of the tour.

Fast-forward to January, when Croft claims Irving Azoff's company -- which she says was handling the Eagles tour at the time -- flew her out to California to do more massage work ... only this time, she claims it became clear it was at Dolan's request.

Basically, she alleges Dolan simply wanted her on the road with him for sex -- and during this stint in L.A., she claims she had an ugly run-in with Weinstein ... who she says was good friends with Dolan, and who she alleges sexually assaulted her at a hotel.

Croft claims she actually ran into Weinstein at the hotel where she was staying -- and once he learned she was Dolan's massage therapist, she alleges he tried to rope her into giving one to him right then and there -- which ended in a chase down the hallway.

Croft claims Weinstein pursued her to her room, and pinned her down and sexually assaulted her ... only to be saved by a phone call from Dolan.

Once Weinstein realized Dolan was on the other end, Croft claims he backed off and said to her ... "Well, you know Jim and I are best friends. He’s going to be very disappointed that you led me on, this won’t look good for you." She claims he then left, and it was over.

Afterward, Croft claims she relayed all this to Dolan himself -- and she says he simply brushed it off ... allegedly noting that he and everyone in Weinstein's circle knew he was a "troubled person" who had "serious issues," and that his pals had tried to get him help.

Croft also points out a song she claims Dolan sent to her other associates years after the fact -- with lyrics that she claims nod to the Weinstein scandal that broke in 2017. It's a real song from his band, called "I Should've Known."

Croft says the lyrics -- which touch on a friend who falls from grace -- are actually a reference to Weinstein, but she claims Dolan knew about him for years.

Croft is alleging she was sexually trafficked, claiming Dolan flew her out to L.A. to continue the sexual relationship, and allowed her to be put in the situation with Weinstein ... an allegation which seems to have opened the door for a federal complaint to be filed.  Of course, she wants major damages.

Dolan is calling this entire suit pure fiction, with an attorney for the mogul telling TMZ ... "There is absolutely no merit to any of the allegations against Mr. Dolan. Kellye Croft and James Dolan had a friendship. The references to Harvey Weinstein are simply meant to inflame and appear to be plagiarized from prior cases against Mr. Weinstein."

His lawyer adds, "These claims reflect an act of retaliation by an attorney who has brought multiple cases against Mr. Dolan and has not won, and cannot win, a judgment against him. Mr. Dolan always believed Ms. Croft to be a good person and is surprised she would agree to these claims. Bottom line, this is not a he said/she said matter and there is compelling evidence to back up our position. We look forward to proving that in court."

Weinstein's own attorney, Jennifer Bonjean tells TMZ … "Mr. Weinstein vehemently denies these meritless allegations and looks forward to litigating these claims in court of law where the truth will be revealed."