The group will retain the acronym Farc - which will now stand for the Alternative Revolutionary Force for the Common People - and adopt a red rose as its symbol.
It was previously known as the Revolutionary Armed Forces of Colombia.
The group finished disarming in June as part of the country's peace process.
About 1,200 delegates from the group met in Bogota this week at the party's first congress since abandoning its five-decade armed cause.
The delegates will choose candidates to run in the 2018 election, where the new party will have a number of guaranteed seats.