From one leaf...that's pretty hard.

Yes, I know. It only has been popping up these leaves all over, single leaves, no flowers, no other foliage. No idea from me.

The sad thing...is I think I've seen it before. But nothing is coming to mind.

all i know.. its a weed...

vaguely reminiscent of a geranium.. and not a good one ... perhaps mallow ... lol ... see above about weed ... lol

you should see the responses i delete.. lol ..

ken

I think mallow, too, at least the overall family. Malva,perhaps?

It looks like a Pennywort.

It is not mallow. In the mallow, the leaf veins begin at point the leaf is attached to the stem, even though the leaves are round, creating a split in the circle.

How big is the leaf? It could be bloodroot. Bloodroot blooms in very early spring without leaves. Then single leaves pop up but don't last very long. before they die off they make a green seedpod that looks sort of like a string bean. It likes deep shade.

Definitely not Bloodroot.

Perhaps a Hydrocotyle sp.

Yep, it's Dollarweed and, as lycopus noted, it's a species of Hydrocotyle. The bane of southern lawns. Check the link below for control measures.

Here is a link that might be useful: Dollarweed

Appreciate the great ID help! Now let me go and remove it from my flower bed!

I love this plant, very soft, very green, downright cute. Too ephemeral to comprise a lawn alone, but welcome to join when ready! Not sure where you are, but USDA lists 5 species known to be present in my state, AL, all natives. If you know where the plant was grown, you could search that state for possible species names, and whether or not they are native.