In human anatomy, the ovum is the largest cell in the body by volume.
A human ovum, also called an egg cell, is typically about 0.1 millimetres across. Unlike most human cells, it is large enough to be visible as a tiny dot without a microscope. Its size provides space for organelles, nutrients and molecular instructions that support the earliest stages of development after fertilisation.
The ovum is produced in the ovaries through oogenesis. Usually, one mature oocyte is released during ovulation, although the precise timing and number can vary. Strictly speaking, the cell released at ovulation is a secondary oocyte; it completes meiosis only if fertilisation occurs.
A common mix-up is confusing the ovum with the sperm cell. Sperm are far smaller in volume but have a long flagellum that helps them move. The ovum is not the largest structure in the body—organs and tissues are vastly larger—but it is the largest individual human cell by volume.