The ratings agency on Wednesday cut the main credit score for banks Credit Agricole, Societe Generale, Groupe BPCE and Dexia from A+ to A. It also lowered ratings for local and regional French governments.
The decision was linked to its downgrade of France's default ratings from the top-tier AAA to AA+ last week. That means the government's "ability to support French banks has decreased slightly," Fitch said in a statement.
France's Socialist government unveiled a modest stimulus plan last week and new measures Wednesday meant to simplify a bureaucracy-heavy, highly taxed economy.
Europe's No. 2 economy is back in recession and facing weak growth prospects.