Charlie Chaplin is generally considered the most celebrated actor of the 1920s. He began his career in the 1914 and made many silent movies until the talking movies were invented, of which the most popular was "The Gold Rush" (1925). He also received a special Academy Award for "The Circus" (1928).
Joseph "Buster" Keaton was another successful actor, both in the United States and in other countries. He is famous for his "Great Stone Face," his trademark --- his face remained completely still and emotionless, no matter what the situation might have been.
Greta Garbo became very popular in America (even before she became involved with actor John Gilbert) who co-starred in movies like "Flesh and the Devil" (1926), "Love" (1927) and "A Woman of Affairs" (1928). She acted both in silent and talking movies, and was forced to take speech lessons to lose her Swedish accent.
Italian-born Rudolph Valentino, the "Latin Lover" of the 1920s, made his debut in 1921 with "The Four Horsemen of the Apocalypse" that won him the spectators' adoration. His death at the age of 31 was mourned on the streets by thousands of people.
Mary Pickford ("Through the Back Door" --- 1921) was called "America's Sweetheart" in the 1920s. People flocked to see her movies, and she became the first millionaire actress at Hollywood. Her marrying Douglas Fairbanks, another movie star, was a major cultural event. She was one of the actresses who couldn't make the transition to the talking movies and retired in the 1930s.
Clara Bow's fame came with the movie "It" in 1927. She was a so-called packaged Hollywood product, an actress that was promoted for a single type of image, limiting her to the same kind of movies. The movie and the actress's publicized romances brought her great success.
Janet Gaynor and Charles Farrell, "America's Lovebirds," started their career together in "Seventh Heaven" (1927). For her role in this movie, Gaynor received the first Academy Award for "Best Actress"; she also received a second Academy Award, the same year, for her role in "Sunrise: A Song of Two Humans."
Joan Crawford (first starring in "Lady of the Night" --- 1925) successfully made the transition from the silent to the talking movies after many elocution lessons. She is one of the few actresses with an impressively long and prolific career (around 50 years and more than 80 movies).