Aimé Auguste Tessier, known as Gaston Tessier was a French trade unionist and Resistance member.
Born in Paris, Tessier attended a Christian Brothers' school. In 1905, he joined the Trade and Industry Employees' Union, a union of Catholic workers, his membership sponsored by Jules Zimheld and Charles Viennet. He became prominent in the union's Study Group, which conducted research into labour-related matters from a Catholic perspective, and he wrote regularly for L'Employé, the union's journal. In 1908, he was appointed as assistant general secretary of the union, then in 1912, he became general secretary of a new union of Christian workers in the Paris region.
As leader of the union, Tessier took a prominent role in founding the French Federation of Catholic Employees' Unions, in 1913, and he was soon also appointed as its general secretary. Due to poor health, he remained in his union posts during World War I, supplementing his income by opening a bookshop.
In 1919, the French Confederation of Christian Workers was established, and Tessier was appointed as its general secretary.