Step 1: Understanding the Concept:
The question asks to identify the most significant Russian playwright of the 20th century.
Step 2: Detailed Explanation:
- Anton Chekhov (1860-1904) is universally regarded as one of the greatest playwrights and short-story writers in history. His major plays, such as The Seagull, Uncle Vanya, Three Sisters, and The Cherry Orchard, written at the turn of the 20th century, revolutionized theatre with their focus on internal drama, subtext, and realism.
- Shakespeare was English and from a much earlier period.
- Stanislavsky was a revolutionary Russian director and acting theorist, but not primarily a dramatist.
- Michael Chekhov, Anton's nephew, was a brilliant actor and acting teacher, not a notable dramatist.
Step 3: Final Answer:
Anton Chekhov is the most celebrated 20th-century Russian dramatist.