Stars, take notice: Josh Groban is doing Broadway right.

In the magical new musical “Natasha, Pierre & the Great Comet of 1812,” which opened Monday, the singer is top-billed. But from his humility, you’d never guess Groban is a multiplatinum recording artist with millions of fans. There’s no ego on display here, only skill.

In composer Dave Malloy’s Slavic-discotheque version of “War and Peace,” Groban portrays Pierre Bezukhov, a stout, middle-aged, unhappily married man with a sorrow he tamps down with philosophy and vodka.

Though Pierre is one of the title characters — and Groban’s name is on the marquee — the sung-through musical really belongs to Denée Benton’s Natasha. Here, in her Broadway debut, the young actress plays a debutante whose fiancé goes off to war; arriving in bustling Moscow, she falls madly in love with the first hot guy she meets. The forbidden fling upends her family and propels her, however briefly, into Pierre’s orbit, since he’s pals with her scorned fiancé. It’s a Romanov rom-com!

And a bold show for Groban to choose. Rather then make his Broadway debut in a tried-and-true musical like “The Music Man,” where he’d be the center of attention, the Grammy-winner jumped aboard “Comet,” a hip, innovative ensemble piece that sends him sprinting through the balcony and playing the accordion.

The brilliant director Rachel Chavkin and designer Mimi Lien have brazenly reconfigured a Broadway theater in ways you’ve never experienced. Malloy’s exhilarating score manages to be both folksy and fit for a dance club at 3 a.m. And in Brittain Ashford and Amber Gray, new Broadway stars are born. And, oh, Josh Groban is with them!

He zig-zags around the entire theater with gusto. Perhaps all those arena tours helped him learn to interact with more than the hundred audience members seated onstage on leather banquettes. Then again, no matter where your seat is, everybody gets a good glimpse of Groban.

Without his star wattage, the unconventional “Comet,” despite its two acclaimed off-Broadway incarnations, might not have made it to the Imperial Theatre. And in signing on to a new musical, he’s enabled exciting young talent to emerge. Groban clearly knows he’s just one of many stars in one helluva great “Great Comet.”