Gwyneth Paltrow is looking back on her romance with Brad Pitt ... including the engagement that never made it to the altar.

Appearing on the "Friends Keep Secrets" podcast, Gwyneth recalled meeting Brad after they were cast together for "Se7en," saying they had a "love at first sight thing" and clicked immediately.

"It was pretty awesome," she said, adding she was 22 at the time and Brad was 31.

Gwyneth said Brad became her first major public relationship right as her own career was taking off ... which meant she was suddenly getting famous for her movies while also being known as Brad Pitt's girlfriend.

She admitted the attention was overwhelming.

The conversation then turned to just how serious they got, with Gwyneth confirming she and Brad were engaged -- a detail that seemed to catch Benny Blanco completely off guard.

"You were engaged to Brad Pitt?" Benny asked.

Gwyneth confirmed it, but said they never made it down the aisle ... explaining she was young and the two were constantly working in different parts of the world.

Benny then joked that it was a "conscious uncoupling" ... borrowing the phrase Gwyneth would famously use years later for her split from Chris Martin.

Turns out, some '90s Hollywood history still has spoiler value.