The largest biological cell is often cited as the ostrich egg, which is about 6 inches (15 cm) long and weigh about 3 pounds (1.4 kg). This is a myth. There are at least several biological cells larger than an ostrich egg, despite the fact that even many scientists and laypeople believe the ostrich egg is indeed the biggest. The ostrich may actually be the heaviest cell, but this has not yet been tested.

Contrary to popular belief, an ostrich egg is not the largest biological cell.

Largeness refers to size, not weight, so the ostrich egg is definitely not the largest. The first type of cell larger than the ostrich egg are nerve cells in especially long animals, such as the Giant Squid and Colossal Squid, which may have nerve cells as long as 39 feet (12 m), about 80 times larger than an ostrich egg. Nerve cells have very long axons, enabling the brain to send signals to distant limbs almost instantly. In giraffes, the nerve cells may be several yards (meters) long, running the whole length of the animal's neck, and in humans, the longest nerve cells are about 4.9 feet (1.5 m), running from the base of the spine to the toes. So even the human body has biological cells larger than the ostrich egg.

Nerve cells in giraffes can be as long as the animal's neck.

One might argue that, in terms of volume, an ostrich egg is still the largest in comparison to nerve cells, which may be very long but exceedingly skinny, on the order of 10 microns or less. Even ignoring nerve cells, however, there is another type of cells larger than the ostrich egg: extremely large algae like Caulerpa, which may grow to 10 feet (3 m) in length or more, a single cell that may include up to 200 fronds.

Caulerpa is one among several other algae that superficially resemble vascular plants because of their branching structure. It is a type of cell that contains numerous nuclei, which may be part of the reason it is often overlooked when the award for largest biological cell is handed out. In Indonesia, certain species are eaten as the "sea grape," and they are said to have a peppery taste, and may be eaten fresh or with sugar.