Horndog ex-New York congressman Anthony Weiner’s seemingly uncontrollable urge to sext could soon get him indicted, as a federal grand jury mulls charges over his online encounters with an underage girl.

The grand jury is expected to begin hearing evidence about the ousted pol’s explicit communications with the out-of-state teen by the end of the month, a law-enforcement source told The Post on Tuesday.

Legal experts have said Weiner’s latest sexting scandal could get him slapped with a federal charge of sexual exploitation of children, which carries a minimum of 15 years in the slammer and a maximum of 30.

It was unclear where the grand jury will convene.

Weiner is under investigation by federal authorities in both Manhattan, where he lives, and North Carolina, the home state of the 15-year-old girl to whom he sent crude messages and shirtless selfies.

Weiner — who formerly disguised himself online as “Carlos Danger” — used the screen name “T Dog” during some of the sexting sessions, which the girl has said began in January and continued through July.

Her dad has called Weiner’s conduct “absolutely criminal,” and predicted: “I’ll be in jail if I come into contact with him.”

​The expected grand-jury probe w​as first reported by the Daily Mail, which also revealed Weiner’s online relationship with the girl.

Weiner’s sexting habit has already cost him a seat in Congress and a comeback mayoral bid.

His wife, top Hillary Clinton aide Huma Abedin, also announced she was leaving him after The Post exclusively revealed​ in August that he sent​ another woman a lewd crotch shot that showed their then-3-year-old son curled up next to him in bed.

Weiner’s troubles have turned him into election-season fodder, with Republican presidential nominee Donald Trump’s campaign calling on Democratic rival Clinton to return $550 in donations from Weiner due to the “extremely disturbing” allegations.

Democratic scion Kerry Kennedy, meanwhile, was recently overheard by a Page Six spy joking that Weiner could make an ideal replacement should Indiana Gov. Mike Pence abandon running mate Trump over his infamous “grab them by the p—y” recording.

“Kerry was like, ‘The Weiner-Trump ticket is the way to go. Weiner can finally be a winner!’” the source said.

Democratic state Assembly candidate Dean Hart of Long Island has also called for legislation to ban adults who sext with minors from “using cellphones and the Internet.”

Weiner, who has not denied sexting with the 15-year-old, didn’t immediately return an email seeking comment.

Weiner has a long history of despicable actions that have led him to this point: