Yes. All rainbows are completely round.
It’s just that we don’t usually see the whole rainbow because we’re standing on the ground and looking toward the horizon.
Unless you’re in the air, or looking down from a mountain, you can usually just see the top part of a rainbow.
The “bow” in rainbow refers to this arch. If you ever see a rainbow, just don’t go chasing for the pot of gold. There isn’t one, unfortunately, we’ve looked.
Rainbows also make for good picture taking, especially on family outings and vacations.