Karlsplatz (German for 'Charles Square') is a town square on the border of the first and fourth districts of Vienna, Austria. It is one of the most frequented and best connected transportation hubs in Vienna. The Karlskirche is located here.

The first district can be reached either by subway (Karlsplatz station) or via Operngasse (a street). The pavilions of the former Karlsplatz Stadtbahn Station remain despite the construction of the U-Bahn system.

The largest area of the square on the south side, Resselpark, is named after the inventor Josef Ressel. To the east is the Karlskirche, located in front of a water pool with a sculpture by Henry Moore with the building of the Vienna Museum (formerly the Historical Museum of Vienna) and the Winterthur Insurance building. On the west side of it is the main building of the Technische Universität Wien (Vienna Technical University) and the Protestant school. In Resselpark, monuments and busts are of famous people such as the inventor Siegfried Marcus and Josef Madersperger, as well as the composer Johannes Brahms. On the north side of the Otto Wagner in Art Nouveau style building erected inclusion of the former station Karlsplatz the Vienna Stadtbahn.

Separated from the plaza to the north are the buildings of the Wiener Musikverein (Vienna Music Society), the Künstlerhaus (art house), and the Handelsakademie (business school). A Video of the plaza and an eventlist are available on the Website of the association karlsplatz.org Verein zur Förderung d. kulturellen Belebung öffentlicher Räume [1].

In the west limit the Secession and the Novomatic Forum (formerly the Office Building), the place that here in the area of the Naschmarkt passes. Near the library building of the University consists Rosa Mayreder Park with the project space Karlsplatz a branch of the Kunsthalle Wien.

Karlsplatz is one of the most important traffic-points of the city, five different traffic flows form a node here:

Before the Karlsplatz was built, there was the decorative Elizabeth Era bridge, built in 1854 and named after the young bride of the Emperor ("Sisi"). The bridge was fitted in 1867 with still images, which now presides over the City Hall stand. On 20 April 1897, it was blocked and subsequently demolished.

Following this, the rescheduling of the bridging of the Vienna River caused long square and fitted with new landmark buildings. On 7 May 1901 the city council established an architectural competition over the new design.