Tạ Thu Thâu (1906–1945) in the 1930s was the principal representative of Trotskyism in Vietnam and, in colonial Cochinchina, of left opposition to the Indochinese Communist Party (PCI) of Nguyen Ai Quoc (Ho Chi Minh).

After a period of uneasy co-operation with "Stalinists" on the Saigon paper La Lutte, he triumphed over the Communists in the 1939 elections to the Cochinchina Colonial Council on a platform that called for radical land reform and workers' control, and opposed defense collaboration with the French authorities.

Tạ Thu Thâu was born in 1906 in Tân Bình, An Phú, (near Long Xuyên) in the French colony of Cochinchina (southern Vietnam), the fourth child of a large and very poor family: his father was an itinerant carpenter.

In April Thâu took part in a week of protests attended by thousands of workers, and by students, sparked by the death, after 18 years penal servitude, of the veteran nationalist Phan Châu Trinh and by the arrest of Nguyễn An Ninh.

Tạ Thu Thâu clashed with Moscow-aligned Communists from the very outset of his political engagement in Paris as a member, and from early 1928 as the leader, of the Annamite Independence Party (An Nam Độc lập Đảng).

"[4] In 1929, after attending a conference of the Anti-Imperialist World Congress in Frankfurt, Germany, and contact with the philosopher and human rights activist, Felicien Challey, and the Communist Party dissidents Alfred Rosmer and Daniel Guérin, Thâu expressed his view of the Indo-Chinese revolution in the Left Opposition La Vérité.

"[2] Arrested during a public protest in front of the Élysée Palace over the execution of the leaders of the Yên Bái mutiny on 22 May 1930, Thâu and eighteen of his compatriots were deported back to Saigon.

Thâu and his associates put forward a "Workers's List" and briefly published a newspaper (in French to get around the political restrictions on Vietnamese), La Lutte (The Struggle) to rally support for it.

In spite of the restricted franchise, two of this Struggle group were elected (although denied their seats), the independent nationalist (later Trotskyist) Tran Van Thach and Nguyễn Văn Tạo, previously a member of the French Communist Party (PCF), now in the PCI.

Colonial Minister Marius Moutet, a Socialist commented that he had sought "a wide consultation with all elements of the popular [will]," but with "Trotskyist-Communists intervening in the villages to menace and intimidate the peasant part of the population, taking all authority from the public officials," the necessary "formula" had not been found.

"[8] With La Lutte now as Tranh Dau (Struggle) an openly Trotskyist paper, Thâu and Phan Văn Hùm led a "Workers' and Peasants' Slate" into victory over both the Constitutionalists and the PCI's Democratic Front in the April 1939 Cochinchina Council elections.

[9] On May 20, 1939, Governor-General Brévié (who set the election results aside) wrote to Colonial Minister Mandel: "the Trotskyists under the leadership of Ta Thu Thau, want to take advantage of a possible war in order to win total liberation."

Hồ Chí Minh had replied, "with unfeigned emotion," that "Thâu was a great patriot and we mourn him", but then a moment later added in a steady voice, "All those who do not follow the line which I have laid down will be broken.

"[22] Up until the capitulation of the South Vietnamese regime to the People's Army of Vietnam and the National Liberation Front in April 1975, streets in a number of southern towns and cities were named in honor of Tạ Thu Thâu.

From March 22, 1955, these included the street leading to the East Gate of Bến Thành Market in old Saigon/Ho Chi Minh City, which now bears the name of the "patriotic intellectual" Lưu Văn Lang.