Heidenheim an der Brenz, or just Heidenheim is a town in Baden-Württemberg in southern Germany. It is located near the border with Bavaria, approximately 17 km south of Aalen and 33 km north of Ulm. 

Annually Heidenheim puts on the Opera Festival "Opernfestspiele Heidenheim" in Hellenstein Castle. The festival developed out of the former serenades held there. Over the past years it has received international recognition and critical acclaim under the artistic direction of conductor Marco-Maria Canonica. During the summer of 2010 all three operas will be performed in full cycles. The Opernfestspiele Heidenheim draws visitors from around Europe and overseas, and has significantly boosted the city's reputation as an important cultural site. Residents also enjoy the annual theater festival in the outdoor Nature Theater.

Every other year the Shepherd Run takes place in Heidenheim, first held in 1723 by Duke Eberhard Ludwig. It attracts all the shepherds in the area. Part of the Shepherd Run festivities is the crowning of a new shepherd king and queen. The Run was held until 1828. After that followed a long break until 1922 when it was held again (five times until 1952). Since 1972 it is once again an integral part of Heidenheim's regular cultural program.

In 2006 Heidenheim hosted the bi-annual Baden-Württemberg State Botanical Show.

Heidenheim annually hosts a World Cup fencing tournament in épée. Because of the size and depth of the field, the Heidenheim event is considered the strongest épée event in the world, stronger even than the World Championships or the Olympic Games.

Schnaitheim is home to the Sasse Theater company.

The State Museum of Württemberg ("Württembergisches Landesmuseum") operates a branch location in Hellenstein Castle where it placed its Carriage and Chaise Museum. The Museum in the Roman Baths exhibits finds dating back to Roman time. The Art Museum, located in a former Jugendstil bath, organizes traveling exhibits. It also displays in permanent exhibit the world's largest and most complete collection of Picasso posters.

Located on top of Hellenstein Mountain and overlooking the city, the most important building and landmark of Heidenheim is Hellenstein Castle.

Notable structures in the inner city are: Protestant Michaels' Church (former parish seat of the city), the Elmar-Doch-House, the Crown Inn and Pub, the Lower Gate, Villa Waldemaier, the burgher tower Türmle, the Castle Pharmacy, the weavers' settlement, the Heathland Smithy, the Old Mint and old Peters' Church (today cemetery chapel).

The construction facility for the manufacture of large turbines built for the local Voith company in 1924 is a significant industrial historic landmark.

The little castle in Schnaitheim is situated at the Brenz river's edge and offers a sight to see for visitors and residents alike. The Schnaitheim Mill is located just a few hundred yards away with its large wheel through operation of the mill was halted several years ago.

In Mergelstetten the old church was torn down in 1841 and replaced with a new, Protestant church built in neo-gothic style. The building was commissioned by Carl Alexander Heideloff who also commissioned Lichtenstein Castle. Lumber was used to build parts of the church because the parish was poor at the time. For the same reason the church tower was not built as tall as originally planned. Nonetheless, this church is popular and picturesque and frequently used on postcards.