Michael Jai White -- Wifey Goes Tat-for-Tat ... Thank You, Black Dynamite! (PHOTOS)

Michael Jai White's wife surprised him with some fresh ink -- getting his initials tatted on her finger ... just to say thank you for an epic love letter he wrote to her.

If you didn't hear about it ... the "Black Dynamite" star pulled off the romantic move of the year -- pouring his heart out to Gillian in a letter which he posted on Facebook ... just to shame every other husband.

We're told Gillian was so moved ... she headed to T-Man Tattoo in Studio City, CA this week to get the sentimental tattoo. It's the same shop where Michael got her initials a few months ago.

Howard Teman, owner of the shop, says the whole thing only took about 15 minutes and cost $90, plus tip. He says Gillian was so touched by Michael's open letter because he's normally very shy.

Smooth move on both their parts. Guys -- read and learn.