Sky Media partnerships director Rachel Bristow is leaving to "take her career in a new direction".
According to an internal memo seen by Campaign, Bristow is leaving the business and a replacement for her role will be advertised in due course.
"After nearly six years at Sky Media, Rachel Bristow has decided to take her career in a new direction," the memo reads.
"Rachel has played an integral part in evolving Sky Media’s partnership offering, our reputation and relationships with media agencies and advertisers.
"She also played a lead part in our transition to Osterley, the move to our new London office and making Sky Media a more inclusive place to work."
Bristow has been one of a relatively small number of senior women in the still-male-dominated world of TV ad sales.
It is thought that it was her decision to leave Sky. Bristow joined in 2014 from Unilever, where she had been vice-president, global media data and analytics.
Her departure from Sky follows a number of senior exits since Comcast's takeover of Sky last year.