Shares in Reckitt Benckiser have fallen after the consumer goods giant announced that Bart Becht would step down as chief executive in September before retiring a year later.
He will be replaced by Rakesh Kapoor, who has been at the firm for 25 years.
Shares in Reckitt, which makes Cillit Bang and Gaviscon, fell more than 6% following the announcement.
Mr Becht is one of the best-paid bosses of any publicly listed company in the world. In 2009, he earned £93m.
This was more than any other FTSE chief executive.
Mr Becht said he felt "honoured" to have led the company, but believed that, "after 16 years in the role, now is the right time to retire".
He praised Mr Kapoor's "outstanding track record" and "broad experience".
Analysts said the market had not expected Mr Becht's departure.
"This is a huge surprise, and is a serious loss to the business. The timing frankly couldn't be much worse," said Charlie Mills at Credit Suisse.
He said the group faced tough trading conditions and increasing generic competition.
Strong growth in developing markets helped Reckitt Benckiser to increase pre-tax profits in 2010 by 13% to £2.1bn, despite lower European sales.
Last year it bought SSL International, the maker of Durex condoms, for £2.5bn to add to its range of brands that include Dettol and Finish dishwasher tablets.