French rescuers reached the distressed boat at about 1 a.m. (0000 GMT) and found that one of its inflatable tubes had deflated. A number of migrants were in the cold waters of the Channel.
Two unconscious people were pulled from the sea. One was airlifted to the French port city of Calais, while the other could not be revived, the coastguard said in a statement.
Search operations were continuing, it added.
The Channel, which separates Britain and continental Europe, is one of busiest shipping lanes in the world.
More than 29,000 migrants have made the perilous crossing in small boats this year, according to Migration Watch UK, representing a fall of about one third in 2022.
In November 2021 at least 27 migrants died after a dinghy sank in the Channel, the highest known number of deaths in a single incident.
(Writing by Richard Lough; Editing by Angus MacSwan)
