The cruising giant told TTG Scott vacated his role on Wednesday (18 March) after more than 10 years.
During his decade-long stint, Scott held several roles before taking on a wider marketing remit last summer.
Before P&O Cruises, he worked for Cable & Wireless, EE, T-Mobile and Orange.
A Carnival UK spokesperson said: "Rob has left the business – he left yesterday."
In 2024, Scott told TTG how P&O Cruises was using brand partnerships to reach "new audiences and disrupt the market".