Ludovic-Oscar Frossard (5 March 1889 – 11 February 1946), also known as L.-O.
Frossard or Oscar Frossard, was a French socialist and communist politician.
He was a founding member in 1905 and Secretary-General of the French Socialist Party (SFIO) from 1918 to 1920, as well as a founding member and Secretary-General of the French Communist Party (PCF) from 1920 to 1922.
On 1 January 1923 Frossard resigned his positions and left the Communist movement over political differences.