Looks like one but hard to confirm through that picture. Fungus gnats thrive when the medium is wet all the time. Are you growing in soil? If so, letting the medium dry out between waterings should do the trick. You could also place some yellow sticky traps by the soil so they get stuck to them and die. I battle fungus gnats every once in awhile and those two things are all I do to combat.
Looks like one to me. Use diatomaceous earth.
So how do you use that?
You should be able to get it from your local box store, it is ground up fossils, that under a microscope, look like little shards of glass that get in between insect joints. When I use it, I just sprinkle it around the plant and put a light cover all around. You can water over top of it and it won't bother it. If it does mix with the soil at all, its ok because it will help against larvae and over time break down as calcium for yer soil. Hope this helps, good growing.