Mastodon Township is a civil township of Iron County in the U.S. state of Michigan.

[3] Mastodon was so named from the fact mastodon bones were discovered when sinking a mine shaft.

[4] Mastodon may have also been named for the size of the large, iron ore body which was struck at the mine site; as "Mastodon" at that time, being a relatively new discovery, was also being used as a slang adjective, meaning large/huge.

[citation needed] The Brule River forms the southern boundary of the township, with the Town of Florence in Florence County, Wisconsin on the other side of the river.

According to the United States Census Bureau, the township has a total area of 135.3 square miles (350 km2), of which 126.6 square miles (328 km2) is land and 8.8 square miles (23 km2) (6.47%) is water.