Kate Hudson, Jennifer Anniston, Julia Roberts, Reese Witherspoon and Steven Speilberg were just some of the big names on the guest list at the Los Angeles Theatre, which the couple hired for their black tie event.
Rumours the the Paltrow/Falchuk wedding would be happening soon have swirled since the bride-to-be received best wishes from friend and designer Giancarlo Giammetti in a sweet social media post during the week.
Sharing a photo of the bride and groom-to-be on Instagram, the Honorary President and co-founder of Valentino said "These two beauties inside and out get engaged tomorrow! All my best wishes my dear Gwynethpaltrow and Bradfalchuk love you and miss not to be there with you!"
The bride-to-be wore a one-shoulder floor-skimming maroon gown to the party, distinctly unlike a traditional wedding dress, and although she has said that she thought she was 'too old' to wear a 'big white dress' for her wedding, it's not thought that the party was her actual wedding party.
According to reports, the lavish party was attended by 400 guests, and was thrown by friend of the couple Ryan Murphy, who created the hit series Glee with the groom-to-be.
The party comes just after the Iron Man star shared snaps from inside her hen weekend in Los Cabos, Mexico, where she was joined by designer Stella McCartney and fellow actor Cameron Diaz, among others.
Sharing a collection of sun-filled photos on her Instagram page, the bride-to-be looked carefree and sun-kissed in the Costa Palmas, which she called 'heaven' in her post.
The couple announced their engagement with a front cover in Gwyneth's GOOP magazine back in January.
"We feel incredibly lucky to have come together at this juncture in our lives when our collective successes and failures can serve as building blocks for a healthy and happy relationship," they shared in a joint statement.
And while the health and fitness enthusiast said she was looking forward to tying the knot, she was keen to 'dial it back' from a big traditional soiree.
"I think I'm (too) old to have a big wedding and a big ole white dress and all that," Gwyneth, who was previously married to Coldplay frontman Chris Martin, said.
"I gotta dial it back."