Seth and Becky announced the big news Thursday over social media ... with Becky calling Seth's beachfront proposal the happiest day of her life.

The super cute couple is definitely moving fast ... they started seeing each other earlier this year, and in May they finally went public with their relationship. Seth and Becky were friends for a while before things turned romantic.

These are some kickass couple ... Seth is the WWE Universal Champion and the WWE RAW Tag Team Champion, while Becky is the WWE RAW Women's Champion.

Looks like Becky is in it for the long haul ... she says they're going to be together for the rest of her life. Seth's been engaged before, but he never tied the knot, and this will be Becky's first marriage.

Congrats!!!