Rose Cohen (Russian: Роза Морисовна Коэн, romanized: Roza Morisovna Koen; 20 May 1894 – 28 November 1937) was an English feminist, suffragist, and founding member of the Communist Party of Great Britain in 1920. She worked for Communist International (Comintern) from 1920 to 1929. Between 1931 and 1937, Cohen served as a foreign editor of The Moscow News. She was executed during the Great Purge in the Soviet Union and posthumously rehabilitated in the Soviet Union in 1956.

Rose Cohen was born in 1894 in London's East End to a family of Jewish immigrants from Łódź, Poland. Her father, Maurice Cohen, was a tailor who later opened his own business and prospered. She was the first cousin of Abraham Cohen and the first cousin once removed of Morris Wartski, both through her father's side. Through the Workers' Educational Association Cohen became well-versed in economics and politics, and fluent in three languages. After leaving the family home, Rose lived with her sister Nellie, Daisy Lansbury and May O’Callaghan in a shared flat on Grays Inn Road, London. In the 1910s, Rose and Nellie became active members of the East London Federation of Suffragettes led by Sylvia Pankhurst. (Nellie worked as Sylvia Pankhurst’s personal secretary). By 1916, British intelligence had placed Rose Cohen under surveillance. Transcripts of intercepted letters and phone calls became publicly available in 2003.

Her education allowed Rose Cohen to get a job at London County Council, where she worked until 1917, and later in the Labour Research Department. She served as a secretary to Beatrice Webb and Sidney Webb. She left the Labour Research Department in 1920. Towards the end of the First World War, the department became the center of the young leftist intellectuals. In his memoirs Maurice Reckitt wrote that Cohen "had great vivacity and charm... and was probably the most popular individual in our little movement..." In 1920 she became a founding member of the Communist Party of Great Britain.

Contemporaries described Cohen as lively, intelligent, educated, and beautiful. Among Cohen's admirers, Harry Pollitt was the most persistent. A photograph of Cohen at the People's History Museum in the United Kingdom was inscribed by Pollitt: "Rose Cohen – who I am in love with, and who has rejected me 14 times."

In the early 1920s, Cohen travelled the world as a Comintern agent. She was assigned secret missions, which included delivering messages and transferring money to Communist parties. In 1922–23 she spent long periods in the Soviet Union, and also travelled to Finland, Germany, Lithuania, Estonia, Latvia, Turkey, France, Norway, Sweden and Denmark. As a Comintern courier, Cohen transferred large sums of money to the Communist parties of these countries.

In 1925, Cohen worked in the Soviet embassy in London and also spent several months in Paris on a secret mission for the Comintern, and handled large sums of money for the Communist Party of France. That year, she met David Petrovsky, whom she later married.

In 1927, following instructions from the Central Committee of the Communist Party of Great Britain, Cohen went to work in Moscow, and in the same year, she joined the Russian Communist Party.

In the beginning of 1929, Cohen married Petrovsky, and in December 1929 she gave birth to their son Alexey (Alyosha). She spent six months that year overseas, traveling to China, Japan, Poland, and Germany on Comintern business.