Neukölln (German: [nɔʏˈkœln] ^ⓘ), formerly Rixdorf (German: [rˈɪksdɔɾf]), from 1899 to 1920 an independent city, is a large inner-city quarter of Berlin in the homonymous borough of Neukölln, and evolved around the historic village of Rixdorf. With 162,548 inhabitants (2025) the quarter has the second-largest population of Berlin after Prenzlauer Berg. Since the early 13th century, the local settlements, villages and cities down to the present day have always been a popular destination for colonists and immigrants. In modern times, it was originally shaped by the working class and gastarbeiters, but western immigration since the turn of the millennium has led to gentrification and a rejuvenation of the quarter's culture and nightlife.

Neukölln is on the North European Plain, which is typically characterized by low-lying marshy woodlands with a mainly flat topography. The quarter lies on the geological border between the shallow Weichselian Warsaw-Berlin Urstromtal glacial valley and the northernmost edge of the Teltow young drift ground moraine plateau, specifically the Rollberge, a small range of glacial hills rising to the south of Hermannplatz and the street Hasenheide, and to the west of Rixdorf and the street Karl-Marx-Straße. Neukölln's average natural elevation is 43.6 m (143 ft) above NHN, ranging from 32.3 m (106 ft) to 54.8 m (180 ft), with the highest man-made elevation at 67.9 m (223 ft) achieved by the Rixdorfer Höhe, a schuttberg in the Volkspark Hasenheide. Neukölln's geographical center, based on a minimum bounding plane, is located east of Richardstraße 101 near Kirchgasse at a linear distance of approximately 2.3 km (1.4 mi) to the river Spree with an elevation of 34.8 m (114 ft).

Neukölln forms the lower east side of Berlin's city center within the Ringbahn, and is the northernmost quarter in the homonymous borough of Neukölln, with the borough stretching all the way to Berlin's southern border with Brandenburg. The quarter, administratively abbreviated Neukö, is officially an Ortsteil, and the borough a Verwaltungsbezirk (administrative district), in Berlin designated Bezirk (district). Different from the borough, the smaller quarter of Neukölln has no mayor or representative assembly of its own. To distinguish the quarter from the borough, the latter is sometimes informally called Groß-Neukölln ("Greater Neukölln"), while the quarter is also called Berlin-Neukölln or Nord-Neukölln.

In the south, the quarter Neukölln is adjacent to the quarter Britz, which is also part of greater Neukölln, and to Späthsfelde in the quarter Baumschulenweg east of Britz. In the north and north-west, it borders on the quarter Kreuzberg in the Friedrichshain-Kreuzberg borough, namely the southern part of the historical Luisenstadt district in the SO 36 neighborhood, and the Graefekiez and Bergmannkiez in the Kreuzberg 61 neighborhood, which were once part of the historical Tempelhofer Vorstadt district. Neukölln's northernmost tip is also adjacent to Kreuzberg's neighborhood Wassertorplatz in the southern part of the historical Friedrichstadt district. In the west and south-west, Neukölln borders on the quarter Tempelhof in the Tempelhof-Schöneberg borough. In the north-east to south-east, Neukölln borders on the quarters Alt-Treptow, Plänterwald and western Baumschulenweg, which, together with Späthsfelde, are all part of the Treptow-Köpenick borough in former East Berlin.

Neukölln is separated from Kreuzberg by the park Volkspark Hasenheide, the Landwehr Canal, and the streets Kottbusser Damm and Hasenheide as far as the city square Südstern, which conforms to Berlin's historical Weichbildgrenze (1861–1919). With Tempelhof, Neukölln shares the Tempelhofer Feld, the vast field of the former Tempelhof Airport, now a popular recreation area. The Britz Canal, the green corridor Heidekamppark with the trench Heidekampgraben, the Kiefholzstraße and several urban streets in the Harzer Kiez separate Neukölln from the quarters of Treptow-Köpenick in former East Berlin. Finally, the Stadtring motorway with the Carl-Weder-Park, streets like Britzkestraße, Juliushof and Grenzallee, as well as the southern end of the Neukölln Ship Canal, form the administrative border with the Britz quarter.

The Teltow Canal, on the other hand, forms the geographical and demographic border within the borough Neukölln. The canal separates the dense urban areas of Neukölln and northern Britz with their higher share of immigrants and lower-income citizenry from the borough's southern residential areas, which, with the exception of Gropiusstadt, are mainly characterized by a larger number of family homes and middle-class households.

Neukölln has nine primary neighborhoods (Kieze), administratively called Ortslagen, among them the historical sites of Neukölln's foundation south-east of the quarters's geographical center,

to the south and south-east of the central plaza Richardplatz, and