Cass, who is currently programme director for Galaxy 102 in Manchester and Galaxy 105 in Yorkshire, takes up his new role this week.
The appointment follows the promotion of Martyn Healy to managing director of Galaxy. Cass will report into Healy.
Cass joined Chrysalis in 1995 as a presenter on Heart 106.2 before taking on a series of programming roles.
He said: "I've spent the past eight years watching the Galaxy brand grow and grow, and this new post will enable me to step up my role in taking it even further going forward."
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