The Sicilian Defense is an opening that commences with the moves 1.e4 c5. The Sicilian Defense is the most popular and best-scoring response to White's first move 1.e4.
For example, 1.d4 is a statistically more successful opening for White because of the high success rate of the Sicilian Defense against 1.e4. New in Chess stated in the 2000 Yearbook that of the games in its database, White scored 56.1% in 296,200 games beginning 1.d4, but 54.1% in 329,855 games beginning 1.e4, mainly because the Sicilian Defense held White to a 52.3% score in 145,996 games.