The average age at which teenagers first have sexual intercourse varies depending on the country, culture, and individual circumstances. According to data from the Centers for Disease Control and Prevention (CDC) in the United States, the average age of first sexual intercourse for females is 17.2 years old, while for males, it is 16.8 years old. However, it is important to remember that not all teenagers engage in sexual activity, and each individual's experience and circumstances are unique.