The living bird that lays the largest eggs is the ostrich.

Largest eggs overall

Ostrich eggs are the biggest of any living bird, typically weighing around 1.5 to 2 kilograms and measuring roughly 15 to 18 centimeters long. They are much larger than the eggs of other big birds like emus, cassowaries, and swans, even though, relative to the ostrich’s own body size, the eggs are proportionally small.

Relative to body size

If the question is about eggs largest compared to the size of the bird’s body, the champion is the North Island brown kiwi. A kiwi egg can be about 15 to 22 percent of the female’s body weight, which is proportionally far larger than an ostrich egg is to an ostrich.