Lauren Conrad throws lavish prom-themed birthday party: ‘This is 40’

On her left arm, the “Hills” alum wore a traditional corsage, and she styled her brunette locks in her signature soft curls.

Other photos showed Conrad’s husband — the guitarist for Something Corporate — taking the stage for a performance, and Lauren posing with various pals as they fêted her milestone birthday.

Several behind-the-scenes photos gave fans a peek inside the intense party prep, including pink and red floral centerpieces, balloons, streamers, and even disco mirror balls going up.

One snapshot revealed a napkin reading “Senior, Senior Prom” and “Party like it’s 1999. Recover like it’s 2026” alongside photo booth-style pics taken at the bash.

“This is 40 ✨ Celebrated with three of my favorite humans @williamtell2nd @leslieannebruce @yashaaramin,” Conrad, who hit the milestone on Feb. 1, gushed in the caption.

“We are all born a few weeks apart, so we threw ourselves a prom to celebrate together. And we had the BEST time!”

“Thank you @lastyoni for the beautiful photos, to the guys in the band for putting together an amazing show for us and to everyone who helped decorate,” she added before quipping, “(And apologies to anyone I just made feel old.)”

Conrad famously attended senior prom at Laguna Beach High in the show’s Season 1 finale, and some of the cast mates who attended alongside her took to the comments thread.

Kristin Cavallari responded, “Yessss 😉,” while Morgan Smith chimed in, “Prom QUEEN Happy Birthday beauty! Can’t believe this year is here!”

Talan Torriero addd, “happy birthday LC” along with an emoji of clapping hands.

Fans also flooded the comments with well-wishes for the fashion designer. “Prom of my dreams! Happy birthday queen,” one person wrote, while another remarked, “The corsage 🤌🏻”

“This is giving Opalite music video vibes 🤩” another person wrote, referencing Taylor Swift’s recently-released retro music video.

The birthday celebration comes just over a year after another big milestone.

In December, 2024, Conrad — along with Stephen Colletti, Dieter Schmitz, Trey Phillips, Morgan Olsen Smith and Christina Schuller Sinclair — got together for their 20-year Laguna Beach High School reunion.