Ettlingen was an important crossroads during Roman times, when the region was part of the province of Germania Superior. This is demonstrated by the many artifacts found in the area, including the "Neptune Stone," which commemorates a flood of the Rhine, and the remains of a Roman bath excavated beneath St. Martin's Church. The city was first mentioned in 788 as "Ediningom" in a deed of donation belonging to Wissembourg Abbey in Alsace (now in France). In 965, the village of Ettlingen ("Ediningom") received market rights (Marktrecht) from Emperor Otto the Great. In 1192, Emperor Henry VI, one of Frederick Barbarossa's sons. Margrave Herman V of Baden-Baden became Ettlingen's feudal lord in 1219. In the following centuries, Ettlingen developed into an important administrative center within the Margraviate of Baden-Baden.
Ettlingen remained an independent city until 1937, when it was incorporated into the administrative unit that would become the district of Karlsruhe in 1939. Ettlingen and its surrounding villages and land has belonged to this district since then.
In 1966, Ettlingen passed the 20,000 population mark and raised to the status of Große Kreisstadt by the state government of Baden-Württemberg. During the communal reforms of the early 1970s, several smaller communities were incorporated into Ettlingen, raising the population to over 30,000. Ettlingen's renowned open-air theater series, the Schlossfestspiele first took the stage in the Baroque inner courtyard of Ettlingen Palace in 1979.
Ettlingen was originally a part of the ancient diocese of Speyer and was under the pastoral care of the Archdeacon of St. German and Moritz in Speyer. The town originally belonged to the deanery of Durlach but was itself made archdiaconate in the 16th century. The Protestant Reformation made gains in Ettlingen as early as 1520, but the town remained mostly Catholic, and the town's Catholic majority was supported by the Catholic line of Baden-Baden; later, starting in 1624, the Jesuits played an active role in converting many of the town's inhabitants back to the Catholic faith. By the beginning of the 19th century, Protestants were a small minority.
During the period of secularization following the dissolution of the Holy Roman Empire, Ettlingen was part of the ordinariate of Bruchsal. In 1821 it became part of the newly-founded Archdiocese of Freiburg, and the town was made the seat of a deanery, which included not only the parishes within Ettlingen proper, but also those in surrounding villages and neighboring municipalities. Today, Ettlingen belongs to the deanery of Karlsruhe, with the various parishes organized into pastoral units (Seelsorgeeinheiten). These include Ettlingen City, with the parishes Herz Jesu (Sacred Heart), Liebfrauen (Our Lady), and St. Martin's, the town's oldest church; Ettlingen South, with St. Dionysius' in Ettlingenweier, St. Wendelin's in Oberweier, and St. Joseph's in Bruchhausen; and Ettlingen Heights, with St. George's in Völkersbach, St. Boniface's in Schöllbronn, and St. Anthony's in Spessart, although Völkersbach belongs politically to the municipality of Malsch.
Jewish families have been living in Ettlingen since at least the 17th century. They lived primarily in Färbergasse ('Dyers' Alley), which was formerly known as "Judengasse" (Jews' Alley). Ettlingen's first synagogue was built on Albstraße in 1849, only to be torn down again when a new synagogue was built on Pforzheimerstraße and dedicated in 1889. The "New Synagogue" was itself destroyed during the infamous Kristallnacht pogrom of November 1938. Most of the remaining Jewish citizens of Ettlingen were deported soon thereafter.
Protestants (Lutherans), most of whom had moved to Ettlingen since the early 19th century, were first administered from Rüppurr, but in 1848 they received their own clergyman, and in 1869 their own parish (Johannesgemeinde - Congregation of St. John), which soon got its own church, the oldest Protestant church in Ettlingen. The Johannesgemeinde belonged to the city deanery of Karlsruhe at first, but was later transferred over to the deanery of Alb-Pfinz with its seat in Pfinztal. The congregation continued to grow and was eventually divided in 1951, creating the Paulusgemeinde (Congregation of St. Paul). The Paulusgemeinde had a parish hall built in 1953, adding a bell tower in 1965. The Paulusgemeinde was itself split up in 1972 to create the Luthergemeinde (Luther Congregation), which caters to the Protestants of Ettlingen West, Bruchhausen, Ettlingenweier, and Oberweier. From 1969 to 2003, Ettlingen was the seat of the Evangelical (Lutheran) Church in Baden's district of Central Baden. However, in the wake of efforts to save money, this district was dissolved and Ettlingen incorporated into the district of North Baden.
Alongside the two major churches, there are also a few free churches and congregations, including a Free Evangelical congregation and the Liebenzell Congregation. The Jehovah's Witnesses, the New Apostolic Church, and a small Jewish community are also represented in Ettlingen.
Ettlingen is a sister city of:
Ettlingen is the location of Rheinland Kaserne. Formerly a German Army base, for many years after World War II Rheinland Kaserne was the home of several U.S. Army units and many Americans who remember Ettlingen fondly. In the mid-nineties, the U.S. Army handed the kaserne back over to Germany. The kaserne is now home to a private school, medical offices, a vehicle registration center, new housing and the Kulisse movie theater.
One of the U.S. Army units which called Rheinland Kaserne home was the 78th Engineer Battalion, then the 44th Signal Battalion.