Which New England colony was established by the separatists?

Plymouth, later part of the Massachusetts Bay Colony, was founded by separatists, who were a Protestant religious group that wanted to separate themselves from the Church of England. They hoped that each congregation could rule its own affairs, apart from the hierarchy of the Church of England. The Pilgrims had been living in Holland, but they decided to settle in the New World in search of religious freedom that they did not have in England.
The Puritans who established the Massachusetts Bay Colony were not technically separatists, though they later joined with the Pilgrims. The Puritans did not separate themselves from the Church of England but sought to purify it from within (thus giving rise to their name). They sought to get rid of Roman Catholic practices and elements within Protestantism.