The company - which accounts for brands including Boohoo, Pretty Little Thing, and Nasty Gal - said John Lyttle would be instated as chief executive from March 15 2019.
He will join from Primark where he currently serves as its chief operating officer, having previously held senior roles at Matalan and the Arcadia Group.
The incoming boss will replace current joint chief executives Mahmud Kamani and Carol Kane.
Mr Kamani will become executive chairman, moving him away from the day-to-day running of the business, while Ms Kane stays on as group co-founder and executive director.
Current non-executive chairman Peter Williams will be stepping down as a result in March 2019, with the board now planning to recruit another independent non-executive director.
Mr Lyttle could pocket as much £1.5 million per year in his new role.
Boohoo confirmed he would receive an annual salary of £615,000 and an annual bonus of up to 150% of that amount.
That is on top of a pension of 5% of his annual salary and a growth share plan.
“John Lyttle’s remuneration package will be heavily related to creating premium growth in shareholder value over the next five years,” Boohoo said in its announcement.
Mr Kamani and Ms Kane said: “We have got to know John over a number of years and are convinced he has the necessary skills to complement what we already have and take the group on to its next stage of growth.
“This is a hugely exciting time for the Group as the fast fashion market continues to shift online and more and more customers across the globe are joining as customers of our brands.”
They added: “The group has experienced exceptional growth over the past few years, with turnover increasing 24 fold from £24.5 million in 2011 to £579.8 million for the year ended February 28 2018, and we believe John is ideally placed to guide the group through the next stage of its growth; whilst he was COO at Primark turnover increased from £2.7 billion in 2010 to £7.1 billion in 2017.
“Our next priority for Boohoo is to ensure we have world class infrastructure and technology in place and we believe John is the right person to lead that journey.”