Charles Xavier Thomas de Colmar (May 5, 1785 – March 12, 1870) was a French inventor and entrepreneur best known for designing, patenting, and manufacturing the first commercially successful mechanical calculator, known as the Arithmometer.

Born Charles Xavier Thomas in Colmar, France, his father was a doctor and member of the town council.

It was during this period that he conceived the idea for the Arithmometer, recognizing the need for a tool to assist with the extensive calculations required for his duties.

Ten years later, in 1829, he started the fire insurance company "Le Soleil" that he grew by merger and acquisitions until his death.

[2][3] Despite this, Thomas spent all of his time and energy on his insurance business, therefore there is a hiatus of more than thirty years in before the Artitometer's commercialization in 1852.