It is the ovum.
Ovum or the female egg cell is the largest cell in the human body.
The smallest cell is the male sperm cell
The size of the largest cell or the female reproductive cell (ovum) varies from about 500 micrometers in radius.
The size of sperm is less than 7 micrometers long.
The combination of these two cells results in the formation of a new human being.
The largest cell in the male is considered to be the neuron. The neuro transmitters which carry signals.
(Image credits: 123rf)