Humans are generally considered megafauna in biology and ecology. The term is based on body mass, not how “impressive” an animal looks.
What megafauna means
In modern ecological usage, “megafauna” usually refers to terrestrial animals above a certain adult body mass threshold, commonly around 45–50 kilograms. Some authors further distinguish “megaherbivores” (over about 1,000 kilograms) from smaller large animals, but all still fall under megafauna.
Where humans fit
Average adult humans typically weigh around 50–80 kilograms globally, clearly above the ~45–50 kilogram cutoff often used for megafauna. Because humans are large-bodied terrestrial mammals in this mass range, many biologists and ecologists treat humans as part of the living megafauna, alongside species like deer, big cats, and smaller bears.
Context in extinction discussions
In discussions of Quaternary and recent extinctions, “megafauna” usually refers to non-human large mammals that disappeared in the last 50,000 years (such as mammoths, giant ground sloths, and diprotodons). In that specific context humans are treated as the primary driver of many megafaunal losses, not as victims, but from a purely size-based ecological perspective humans themselves still qualify as megafauna.