The largest known bacteria is Thiomargarita magnifica. It was discovered in 2022 and can grow up to 2 centimeters (0.8 inches) in length, which is visible to the naked eye.

Previously, Epulopiscium fishelsoni was considered the largest bacteria, with a size reaching up to 0.5 millimeters in length.

However, *Thiomargarita magnifica* is significantly larger than *Epulopiscium fishelsoni*, making it the undisputed champion of the bacterial world in terms of size.