Karel Müller was born in Ostrava in 1958. After graduation in History from the Faculty of Arts of the Palacký University Olomouc in 1982, he started to work at the Regional Archive in Opava. He works here till now.
He became a director in 1990. His work and publications are focused on Auxiliary Historical Sciences (Heraldry, Sigillography, Genealogy) and sources of history of Silesia.
He is a member of the Subcommittee for Heraldy and Vexillology of the Chamber of Deputies of Parliament of the Czech Republic since 1991. He lectures on Heraldry and sigillography at the Silesian University in Opava, till 2010 did it also at Palacký University Olomouc