Mixed-sex education, also known as mixed-gender education, co-education, or coeducation, is a system of education where males and females are educated together. Whereas single-sex education was more common up to the 19th century, mixed-sex education has since become standard in many cultures, particularly in western countries. Single-sex education remains prevalent in many Muslim countries. The relative merits of both systems have been the subject of debate.

Education is the transmission of knowledge, skills, and character traits and manifests in various forms. Formal education occurs within a structured institutional framework, such as public schools, following a curriculum. Non-formal education also follows a structured approach but occurs outside the formal schooling system, while informal education entails unstructured learning through daily experiences. Formal and non-formal education are categorized into levels, including early childhood education, primary education, secondary education, and tertiary education. Other classifications focus on teaching methods, such as teacher-centered and student-centered education, and on subjects, such as science education, language education, and physical education. Additionally, the term "education" can denote the mental states and qualities of educated individuals and the academic field studying educational phenomena.