Colette Paul joined South Wales Police from the Met two years ago
The assistant chief constable at South Wales Police is being promoted to become second in command.
The force has announced Colette Paul will become deputy chief constable on New Year's Day.
The 49-year-old has been a police officer for 25 years starting her career with the Met before moving to South Wales two years ago.
She will join new chief constable Peter Vaughan in leading the force into the next decade.
Ms Paul was one of three candidates interviewed for the position.
Since joining South Wales Ms Paul has been leading the protective services portfolio, which covers crime, specialist operations and intelligence, along with the force's Olympics preparations.
She has also had regional responsibility for terrorism and counter-terrorism.
She said: "Since joining this force two years ago I have been overcome by the warmth and friendliness of all those who live here.
"I am incredibly proud to have been chosen to help lead this force into the next decade.
"This position is really challenging, but a fantastic opportunity to develop links and work with other public authorities across Wales to provide everyone here with the best possible service."
Police Authority chairman Russell Roberts said: "Colette is an exceptional police officer and the authority is very pleased to appoint her.
"Her knowledge and understanding of policing is outstanding and complements that of our new Chief Constable Peter Vaughan."