Andrea Costa (29 November 1851 – 19 January 1910)^[1] was an Italian politician^[2] who was initiated on September 25, 1883 to the Masonic Lodge "Rienzi" in Rome and progressively become 32nd-degree Mason^[3] and adjunctive Great Master of the Grande Oriente of Italy.^[4][5]

Costa was arrested in the failed Bakuninist 1874 Bologna insurrection as its main Italian organizer.^[6] Costa left the country and was arrested in France. He continued to agitate in Romagna.^[7] In a letter, "To My Friends and to My Adversaries", he defended himself against charges of reformism or anti-revolutionarism but effectively broke from his anarchist past.^[8] The Russian socialist Anna Kulischov, who had met Costa in Paris in 1876 and was another former Bakuninist, is believed to have spurred his transition from anarchism to socialism.^[9]

Costa founded the Revolutionary Socialist Party of Romagna in 1881 with a small regional following.^[10] Costa became the first Italian socialists elected to the Italian Parliament the next year. In 1892, he called the Genoa Congress, which established the Italian Workers' Party, which was later renamed as the Italian Socialist Party.^[9]

He was later a politician and mayor of Imola and died there in 1910.^[11]

His close friend and masonic brother Giovanni Pascoli wrote the funeral inscription dedicated to him,^[4] whom he knew together with Alceste Faggioli when he was a university student.^[12][13]

The parents of Benito Mussolini gave him the middle name "Andrea" in Costa's honour.