Carol Marlow and Peter Shanks will both be leaving P&O Cruises and Cunard Line at the end of September.
Their departures are part of a major shake-up at the cruise lines.
Under Gerard Tempest, now six months into his role as chief commercial officer, a new organisation sees the creation of two new marketing director roles, one for each brand.
There will also be a new position of insight director covering both brands.
Parent company Carnival said the recruitment of these three new roles is already at an advanced stage and a further announcement will be made shortly.
Tempest said the decision to get rid of the MD positions was taken after very careful consideration.
"On behalf of everyone at P&O Cruises and Cunard, I would like to thank both Carol and Peter for their very significant contributions to the success of the business over many years and wish them every success in their future endeavours."
Marlow joined P&O in 1997 and over her 16 years has led a number of brands including Swan Hellenic, Princess Cruises UK, Cunard and P&O Cruises.
Shanks joined in 2002 and has held "pivotal" leadership roles within Cunard, Ocean Village and Princess Cruises UK.
Last month, Carnival UK announced its sales and customer service director Giles Hawke is leaving the company in November to take up a new role within the cruise sector.
The high profile director was with Carnival for 10 years.
by Bev Fearis
