The combined company will be named Thomson Airways and offer flights to all destinations currently served by the two airlines.
Parent company TUI announced the change this week, revealing that the merger will create the third largest airline in the UK.
Both First Choice and Thomson will continue to operate as high street brands, though all aircraft will be rebranded to Thomson Airways over the next two years.
Chris Browne, managing director of the new airline, said: "Our aim is to build on the very best from these two award-winning airlines that share a very strong drive to provide a truly exceptional customer experience.
"By incorporating both airlines under one name, we will now operate 65 planes to over 80 destinations from 21 airports in the UK."
Meanwhile, Thomsonfly has announced new flights to Tel Aviv as part of its winter schedule. The carrier will operate three flights a week from Manchester and Luton to the Israeli city.
Commenting on the new flights, the airline’s commercial director Guy Stephenson, said: "Tel Aviv has a growing reputation as a stylish and lively choice for city breaks, but also as an important destination for cultural exchanges between schools and religious groups, religious and history-based leisure breaks, visiting friends and relatives and as a place for doing business."