Kanye West Posts Video of Bianca Censori Naked in Bathtub on Her Birthday

Bianca Censori is taking the term "birthday suit" to heart ... 'cause her man Kanye West posted about her on her special day -- and, she's totally naked in the clip!

Censori turned the big 3-0 Sunday ... and, in her honor, Ye took to IG to post several videos -- including this one featuring Bianca soaking wet in the bathtub, completely nude with her hair slicked back.

She's clearly talking in the vid ... but, Ye has distorted the audio -- so, it's impossible to make out what she's saying.

Ye captioned the clip, "happy birthday baby" ... a loving tribute to the woman he reportedly married about two years ago.

Kanye -- who posts very sporadically on IG BTW -- decided to double up in his lady's honor ... posting a video of Bianca dancing with a major star.

In the video, Bianca is chest to chest with like Academy Award winner Penelope Cruz ... moving and grooving in the middle of a hyped up dancefloor.

It's unclear when this clip was taken ... but, Ye tagged both Bianca and Penelope in the caption -- adding, "happy 30th" to the caption.

As you know ... Kanye hasn't exactly been in Hollywood's inner circle recently -- after his antisemitic comments sparked outrage among the public. But, with Penelope openly embracing Bianca, it's clear not everyone has cut ties with the couple.

Anyhoo ... happy birthday, Bianca! That birthday suit fits ya just right!