The authority will soon begin its search for a deputy town clerk.
Ms Mann said: “I feel greatly honoured to have been appointed as the new town clerk of Malmesbury and I look forward to supporting the council with its vision for the town and its community.
“Malmesbury is a fascinating place with a pioneering council that seeks to do the very best for those it represents and I keenly anticipate working with its residents and the town council.”
Chairman of the personnel subcommittee, Wayne Jones said: “I am delighted that full council approved the appointment of Ms Claire Mann to the post of town clerk at its meeting on Tuesday evening.
“Claire has been with the council for several years, including as our deputy town clerk for the last two years, and is a valued member of the team.
“Since March Claire has routinely demonstrated her ability to lead and steer this council.
“As a local person, Claire is naturally passionate about our town and community, and I am sure will continue to serve in the positive and engaging manner she has displayed throughout her employment with the town council.”