Credit: Splash News Online

Justin Timberlake really, really loves Jessica Biel -- and she's got the giant engagement ring to prove it!

After months of secrecy, the New Year's Eve actress (in a Twelfth St by Cynthia Vincent dress and a jacket by TheEternal) finally debuted her giant rock in public at The Tavern in L.A. Thursday. She was joined by Timberlake, 31, who popped the question over the holidays in Jackson, Wyoming.

Biel first gave off a glimpse of her ring at a Saturday Night Live afterparty at New York City's Ristorante Asellina on February 18. "It looked vintage and might have been custom made," a witness told Us Weekly. Despite showing it off to Amy Poehler and Kristen Wiig, Biel managed to keep her new bling hidden from photographers.

Timberlake and Biel, who have been together on-and-off for nearly five years, are planning to wed "this summer at a private estate," an insider recently told Us, who added that Biel is hoping to wear Monique Lhuillier for her big day.

Though neither star has talked publicly about their engagement, Biel's New Year's Eve and Valentine's Day director Garry Marshall recently admitted they've spoken at length about her happy news.

"We talk about it a lot. I hope it all works out -- they are terrific kids," Marshall told Us of Biel, 30, and Timberlake. "I love them both. I'm happy for her."