What is the name of the Cybermen's home planet?

The Cybermen’s original home planet is Mondas. In their first appearance, the 1966 serial “The Tenth Planet,” Mondas is revealed as Earth’s long-lost twin, with matching continents and a similar history.

Mondas was knocked out of its orbit and drifted through deep space. To survive, its inhabitants replaced much of their biology with machinery, eventually becoming the emotionless cyborgs known as Cybermen. The planet later returned to the Solar System, where it began draining Earth’s energy; the resulting imbalance destroyed Mondas and the Cybermen stationed there.

Telos is sometimes confused with Mondas because it became an adopted Cyberman base and was central to stories such as “The Tomb of the Cybermen.” Gallifrey is the Doctor’s home planet, while Skaro is associated with the Daleks. Later Doctor Who stories introduced alternate Cyberman origins, but Mondas remains the classic answer.