Gymnasium (German pronunciation: [ɡʏmˈnaːzi̯ʊm]; German plural: Gymnasien), in the German education system, is the most advanced and highest of the three types of German secondary schools, the others being Hauptschule (lowest) and Realschule (middle). Gymnasium strongly emphasizes academic learning, comparable to the British sixth form system or with prep schools in the United States. A student attending Gymnasium is called a Gymnasiast (German plural: Gymnasiasten). In 2009/10 there were 3,094 gymnasia in Germany, with c. 2,475,000 students (about 28 percent of all precollegiate students during that period), resulting in an average student number of 800 students per school.

Gymnasia are generally public, state-funded schools, but a number of parochial and private gymnasia also exist. In 2009/10, 11.1 percent of gymnasium students attended a private gymnasium. These often charge tuition fees, though many also offer scholarships. Tuition fees are lower than in comparable European countries. Some gymnasia are boarding schools, while others run as day schools; they are now predominantly co-educational, and few single-sex schools remain.

Students are generally admitted at 10 years of age and are required to have completed four years (six in Berlin and Brandenburg where they are enrolled at the age of 12) of grundschule (primary education). In some states of Germany, permission to apply for gymnasium is nominally dependent on a letter of recommendation written by a teacher or a certain GPA, although when parents petition, an examination can be used to decide the outcome.

Traditionally, a pupil attended gymnasium for nine years in western Germany. However, since 2004, there has been a strong political movement to reduce the time spent at the gymnasium to eight years throughout Germany; nowadays most pupils throughout Germany attend the gymnasium for 8 years (referred to as G8), dispensing with the traditional ninth year or oberprima (except in Rhineland-Palatinate and Lower Saxony which still has a year 13; Bavaria will bring back the 13th year in 2024, North Rhine Westphalia and Schleswig Holstein will bring back the 13th year in 2025), which is roughly equivalent to the first year of higher education. Final year students take the abitur final exam.