Charles Otto Trechmann was born in Hartlepool on March 19, 1851, the eldest son of Peter Otto Edward Trechmann, a Danish immigrant who established a cement factory in northern England in 1848. After a preliminary education at the Grammar School in Richmond, Yorkshire, he attended the Polytechnic School in Hanover, then entered the University of Heidelberg where he studied chemistry for two years under Bunsen and earned his PhD. Returning to England, he joined his father's business and managed it very successfully. He was also Managing Director of two other family businesses (Trechmann, Weeks & Co. Ltd. and the Purfleet Chalk Quarries in Essex), and served for many years as Justice of the Peace for the borough of Hartlepool.

While in Heidelberg he acquired an interest in mineralogy and crystallography, and began building a collection, working on it at every opportunity for the rest of his life. Despite his busy business and public schedule he also found time to publish 20 scientific papers, most of them dealing with crystallographic subjects, especially regarding the minerals of the Binn Valley in Switzerland. By the time of his death his mineral collection numbered about 5,000 choice, well-crystallized specimens housed in two well-made cabinets in his home, called Hudworth Tower, in Castle Eden.

He died on June 29, 1917, bequeathing part of his collection to the British Museum and part to his son, Dr. Charles Taylor Trechmann, who later donated more of the specimens to the same institution. The mineral trechmannite was named in his honour in 1905.