List of by-elections to the 15th National Assembly of France

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.

Cumulative results
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. The classification of candidates and changes are based on the classification of candidates at the time. For example, in the 2018 by-election for French Guiana's 2nd constituency, Davy Rimane was classified as a regionalist candidate in 2017 and a candidate of La France Insoumise in 2018 (and a comparison therefore made with 2017 candidate Paul Persdam); in addition, Ramlati Ali was classified as a Socialist Party candidate in 2017 and miscellaneous left in 2018.

Pas-de-Calais's 6th constituency
Pas-de-Calais's 6th constituency is vacant since 27 September 2020.

Paris's 15th constituency
MP for Paris's 15th constituency George Pau-Langevin resigned.

Indre-et-Loire's 3rd constituency

 * Indre-et-Loire's 3rd constituency

Oise's 1st constituency
Olivier Dassault died suddenly in March 2021. He was succeeded by his nephew Victor Habert-Dassault.

Indre-et-Loire's 3rd constituency
Sophie Métadier was elected in Indre-et-Loire's 3rd constituency