Swizz Beatz Gifts Alicia Keys Pricey LEGO-Themed Link Chain

Alicia Keys is legit OBSESSED with LEGOs ... and no one knows this better than Swizz Beatz, who dropped a king's ransom to gift her a colorful and ritzy LEGO-themed chain.

Celeb jeweler Elliot Eliantte tells TMZ ... Swizz reached out and said he wanted a one-of-a-kind chain worthy of Alicia's love for LEGOs -- plus it was for her 40th, so it had to be special.

As diehard Alicia fans know, building LEGOs is one of her favorite hobbies -- so what's better than a LEGO-themed link chain including her favorite colors?? Eliantte says he used around 65 carats of diamonds and sapphires to make it happen.

He's not saying how much Swizz dropped, but our sources say it's worth at least 6 figures. Important note: while the gems were arranged in LEGO form ... no actual LEGOs were used in the chain. Sorry, Alicia. 😔

It's okay, though ... one of her other bday gifts -- she turned 40 on January 25 -- was a Statue of Liberty LEGO set!!!