Yes you can keep gravy in the fridge.
You can place gravy in some sealed containers or Ziploc bags and then place them in the refrigerator.
The gravy will keep in the fridge or refrigerator for up to 5 days before it goes bad.
If you want to keep the gravy longer than a few days it's better to freeze the gravy instead.
When you freeze the gravy the gravy will last for up to a year.
However the longer the gravy stays frozen in the freezer the less tasty it becomes and it loses it's quality and freshness.
But the gravy will remain safe to eat as long as it's been frozen even for 2 years and longer.