RYAN SEACREST dumped JULIANNE HOUGH because of her wild partying and boozing!

The head-turning cou­ple first hooked up in 2010 and have struggled to keep their romance on track, in part due to their busy careers.

But Ryan, 38, has finally grown to realize that Julianne is too much of a party girl for him – and sources say that’s the REAL rea­son he gave the 24-year-old blonde beauty her walking papers in mid- March.

“Ryan tried his best to keep up with Julianne, but in the end he just couldn’t,” said a source. “He’s older, al­ready established and set in his ways, and he was getting tired of telling her to lay off the alcohol and stop overin­dulging.

“They constantly fought because he wanted her to slow down and she wanted him to lighten up and enjoy life more.”

According to sources, it wasn’t un­usual for the “American Idol” host to go home early and let the former “Dancing with the Stars” pro stay out with her friends until the sun came up.

And Ryan was said to be pushed to the edge last summer when Julianne was photographed leaving the Lon­don nightclub Roka “wobbly and bleary-eyed” after the premiere of her film “Rock of Ages.” The dancer-turned-actress was spilling out of her dress, unsteady on her feet and had to be escorted out of the club and helped into a car.

More recently, Julianne shocked onlookers at a Jan. 13 Golden Globes bash when she danced the night away even after ripping her design­er gown up to her thighs.

“Ryan sat Julianne down and told her he couldn’t stand to watch her throw her life away,” said the source.

“He cares for her deeply, but he felt like she was forcing him to act more like a parent than a husband-to-be.”

A rep for Juliann has denied that her alleged hard partying cause the couple’s split.