This is a robber fly (Diptera: Asilidae). Robber flies are considered beneficial predators in our landscapes.
From the University of Florida: There are >7,000 described species of Asilidae worldwide and nearly 1,000 in North America.
All robber flies have a characteristic divot on top of the head, which is located between their especially prominent compound eyes. Generally, adult robber flies have an elongate body with a tapered abdomen, but there are some variations. Robber flies have long, strong, bristled legs with which to capture prey. Most robber flies have brown, gray, or black coloration.
Robber flies capture prey in flight and inject their victims with saliva containing neurotoxic and proteolytic enzymes. The injection rapidly immobilizes prey and allows digestion of bodily contents. The robber fly soon has access to a liquid meal, which is generally consumed upon returning to a perched position.