The sexy stars hold each other arm-in-arm.
The gorgeous actors enjoy a date night.
The lovebirds strike a pose.
Looks like it's Costner's significant other who steals the spotlight, arriving in a gorgeous hot pink outfit.
The couple put on their best smiles for their red carpet pose.
The happily engaged couple are all smiles arriving to the SAG Awards red carpet.
The Downtown Abbey star and his girlfriend stun on the red carpet.
The couple arrive hand-in-hand to the red carpet.
The mom-to-be looks elegant in her purple gown and with her man by her side.
The couple look polished in their ensembles for the SAG Awards.
The duo—or should we say soon-to-be family of three—look great matching in black.
MORE PHOTOS: Stars' Instagrams from the 2015 SAG Awards