By-elections to for the French National Assembly are held within three months after the invalidation of the election or resignation of a deputy.
No by-elections are held within the twelve months of the end of a parliamentary cycle.
Eight by-elections have been called since the inauguration of the 15th legislature of the French Fifth Republic.
The changes displayed within the table below compare the results of by-elections up to the end of September 2018 to the outcome of the 2017 legislative elections within the constituencies where by-elections had been held till then.
MP for Paris's 15th constituency George Pau-Langevin resigned.