The US firm will provide Team Britannia – which will embark on a 23,000-mile voyage from Gibraltar in March – with everything they need from shoes to jackets.
The announcement was made by team principal Alan Priddy, following the successful operation to turn over the 80ft hull of the boat, marking the final leg of construction.
Mr Priddy said: ‘I have always loved Sebago and have used it on many of my world record voyages.
‘What sets them apart is their belief in sticking with traditional skills and craftsmanship.’
Maria Vasconcellos, Sebago UK’s marketing manager, said: ‘We are delighted to be supporting Alan and the crew as their official clothing and footwear providers.’
Team Britannia hopes to beat the fastest time set for circumnavigating the globe, currently held by New Zealander Pete Bethune at 60 days 23hrs 49mins.