Engaged! Laura Prepon flashes diamond ring as she makes red carpet debut with fiancé Ben Foster 

Laura Prepon and Ben Foster are engaged.

And on Tuesday the beauty, 36, showed off her diamond engagement ring from the actor as they posed at the premiere of Prepon's new thriller The Girl On The Train in New York.

He was last engaged to Robin Wright, the ex of Sean Penn. 

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It's official! Laura Prepon made her red carpet debut with boyfriend Ben Foster on Tuesday and also sparked rumours she's set to marry the Alpha Dog star as she flashed what appeared to be an engagement ring

It's official! Laura Prepon made her red carpet debut with boyfriend Ben Foster on Tuesday and also sparked rumours she's set to marry the Alpha Dog star as she flashed what appeared to be an engagement ring

Bling: A look at her engagement ring

Bling: A look at her engagement ring

Laura looked stunning in a lace teal pencil dress, black heels, a smattering of Forevermark diamonds and a matching clutch.

She showed off the significant piece of jewelry - a gold band with large solitaire diamond - as she linked arms with the Warcraft star. 

Rumours that the couple were dating first emerged earlier this summer when they were pictured out in New York together.

Us Weekly reported in July that the twosome were spotted making out at French bistro Lucien. 

Hot new couple: The duo were first rumoured to be dating after being spotted on PDA-filled dates in July

Hot new couple: The duo were first rumoured to be dating after being spotted on PDA-filled dates in July

Knock their socks off like Laura in a lace dress by Nha Khanh

Laura Prepon might have been sporting a huge diamond on her ring finger when she attended the New York premiere of The Girl On The Train, but it was her dress that really dazzled us!

The red carpet event was a glamorous affair, with Emily Blunt wearing a green Prada gown and Haley Bennett rocking a ruffled dress by Altuzarra. But you can never go too far wrong with a little lace number like Laura's.

It's by Nha Khanh and we love the chic shade of teal. The sleeveless style, midi length and vertical stripe on the top half elongates the figure, and when teamed with a black box clutch and pointed heels, it's a great look.

Unfortunately this AW16 piece isn't available online, but click (right) to shop the collection over at Saks Fifth Avenue. Or go green on your next night out in one of the lookalike lace dresses we've got lined up for you in the edit below.

* PRICES MAY NOT BE AS ADVERTISED

Ben, 35, was most recently engaged to House Of Cards star Wright, 50.

The couple, who had dated for more than three years, quietly ended their engagement for a second time last year.  

Ben and Robin first broke up in November 2014 but got back together shortly after.  

Meanwhile, Laura hasn't been reported to have been in a serious relationship since her 2007 split from actor Christopher Masterson, the brother of her That 70's Show co-star Danny Masterson.

The Mastersons, like Prepon, are Scientologists. Last year in an interview Prepon called Scientology practices 'like magic' and credited the church with helping her acting. 

Raven haired beauty: The 36-year-old actress looked gorgeous in a sheer teal pencil dress and black heels
Raven haired beauty: The 36-year-old actress looked gorgeous in a sheer teal pencil dress and black heels

Raven haired beauty: The 36-year-old actress looked gorgeous in a sheer teal pencil dress and black heels 

Romance blossoming: The actors are pictured out together in New York on June 21

Romance blossoming: The actors are pictured out together in New York on June 21

Interestingly, Ben and Laura are both pals of Danny's and it's rumoured that the mutual friendship is how the couple met. 

In 2014 Laura lamented her lack of luck in the romance department.

'When I'm working, it's next to impossible,' she told Cosmopolitan in 2014 as she confirmed her single status. 

'I like to think I'll just be walking down the street one day and stop and meet someone, like, "Oh, my God, you're awesome," and then we start dating. But, no.'

'Guys occupy a lot of attention space in your mind,' she added. 'When I'm working, living in a new place, it's kind of cool I don't have to deal with that.'

Didn't work out: Foster, 36, split from fiancee Robin Wright, 50, last year 

Didn't work out: Foster, 36, split from fiancee Robin Wright, 50, last year 

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