Marshall, the 55-year-old chief constable presently the chief executive of the College of Policing, the professional body for police in England and Wales, will assume charge at the ICC from September.
Marshall began his career as a police officer in 1980. He was appointed Chief Constable of Hampshire in 2008, and was selected to head the new College of Policing when it was created in 2012.
Commenting on his appointment, ICC ACU chairman Ronnie Flanagan said, "I am very pleased to announce the appointment of Alex Marshall as the new General Manager of the ACU."
"Marshall brings with him from his distinguished police career, a tremendous wealth of knowledge, expertise, experience and commitment which I know will further bolster the ACU in its fight against corruption in cricket," he added.
A self-proclaimed cricket fan, Marshall said: "I am a life-long cricket fan and am very keen to play my part in keeping my favourite sport clean. My police career has taught me the importance of prevention and education, operating to clear standards, making best use of intelligence and prosecuting where appropriate."
"I see these approaches as equally applicable to my new role in the ICC which I relish taking up in September. Until then I, of course, remain fully committed to my role at the College of Policing," he added.