Arsenal Technical High School, commonly referred to as Tech or Arsenal Tech, is a public high school in Indianapolis, Indiana, United States, which is run by the Indianapolis Public Schools district. The school is located on a 76-acre (31 ha), multiple building campus east of downtown Indianapolis, and is the only such type school in Indiana.

The school's campus originally served as a U.S. Civil War era arsenal from 1864 until 1903, when it was closed following the Spanish–American War. A few years later, the school opened in 1912 under founder Milo H. Stuart. A number of extant buildings dating back to military use are still open and serve academic purposes for the school, such as the Arsenal building and the Barracks. In addition, a number of additional buildings were built in the following decades to accommodate the school's functions. Due to the significance of the school's campus, facilities, and history, Arsenal Technical was placed on the National Register of Historic Places in 1976.

Arsenal Technical offers four academic programs at the school. These include the New Tech program, the Math and Science program, the Law and Public Policy program, and the Career Technology Center.

Arsenal Technical High School, once a United States Arsenal, includes a Civil War armory complex and 20th-century buildings on its campus. The campus has dual significance as the oldest military installation in central Indiana, and the third oldest high school in Indianapolis (of which it is the second oldest high school to still operate at its original location).

Following the election of Abraham Lincoln to the presidency of the United States, the prospect of civil war was evident. Indiana governor Oliver P. Morton ordered the temporary creation of an Indiana arsenal in 1861 on the present grounds of the Indiana State House. However, it soon became clear that the location would not suffice, and in 1862, Congress passed an act "providing for a permanent National Arsenal at Indianapolis". The current location was chosen by army planners because it had close access to downtown Indianapolis, but was also far enough outside the city limits that it would not disrupt any neighborhoods.

The first soldiers arrived in 1865. The location was used to store heavy artillery, lighter arms, and some munitions, and was maintained by the United States government until 1903. About fifteen different commanders and fifty soldiers were stationed at the Arsenal during its years of operation.

After the Spanish–American War, arsenals were considered obsolete for military needs, and there was a nationwide trend towards their abandonment; in addition, the city of Indianapolis had fully encroached on the site at the time. As a result, in 1903, the title to the Arsenal grounds was sold at public auction to an Indianapolis public trust, which aimed to keep the property intact as the site of a school or park.

In 1904, the Winona Agricultural and Technical Institute established an Indianapolis school on the site. The Indianapolis public trust planned to execute the deed to the Institute upon proof of sufficient endowment; however, a 1909 investigation made it clear that the institute was insolvent. As a result, a case was filed and venued to the Hendricks County Circuit Court by the Indianapolis public trust. Following years of litigation, including an appeal to the Indiana Supreme Court, a 1916 ruling gave the site to the Indianapolis Public Schools district, which had expressed interest in the site.