Steven Tyler Engaged?! — Dude Looks Like a Fiance

Steven Tyler is domesticating himself  … because his longtime GF was sporting a huge rock on her finger this weekend … and sources close to the rocker tell us it’s an ENGAGEMENT RING!

63-year-old Tyler and 38-year-old Erin Brady hit Maui on Xmas day … along with a massive new diamond. It’s unclear if Tyler proposed before or during the tropical vacay.

The two have been dating since 2006.  Tyler has been married twice before … he married a model in 1978 and a clothing designer in 1988.