GSP Belgrade (Serbian: ГСП Београд, romanized: GSP Beograd) is a public transit company for the city of Belgrade. As of 2018, it operates with 170 lines and has 1,611 active vehicles.^[4]

The acronym "GSP" stands for Gradsko saobraćajno preduzeće (Градско саобраћајно предузеће, English: City Transport Company).

Its history dates back to 14 October 1892 when the first horse tram line began operating in Belgrade between Slavija and Terazije. It was known under the name Beogradska varoška železnica (Београдска варошка железница, English: Belgrade City Rail).^[5] The first bus line was opened in 1925 and in 1947 the first trolleybuses appeared in Belgrade.

In 1940, the tram traffic took place on 10 lines. Belgrade has disposed of 104 trams, 60 trailers and 87 buses. The following year, in the bombing of Belgrade was destroyed 38 trams, 36 trailers and 10 buses. In 1945, company changed its name to the Department of traffic lights and the Executive Committee of the City of Belgrade. In Belgrade Radio 4 tram and bus lines 3 with a total of 58 vehicles. In 1947, the first trolley was introduced to the line Kalemegdan - Slavija.

In 1955, in Belgrade was 8 tram lines with 162 trams, three trolley lines with 42 trolley buses and 14 bus routes with 148 buses. In 1956, he was released into operation first trolleybus domestic production - "Goša FOM". Belgrade and Zemun are associated trolley lines. As of 1960, there was 38 lines (7 tram, 6 trolleybus and 14 bus). Number of vehicles in inventory stood at 467. In 1961, 160 "Leyland" buses were purchased.

In 1962, cab vehicles were introduced, a total of 63 vehicles. In 1970, 144 new vehicles were purchased for the transport of Belgrade. The total number of vehicles has increased to 806. In 1975, new zonal tariff system was introduced and number of vehicles rose to 995. By 1985, the total number of vehicles was 1380, and the average number of vehicles in traffic in operation was, on weekdays was 779. In 1989, an integrated system of unified tariff system, in addition to Lasta and GSP in the system is turned on and ZTP Beograd and ATP Pancevo.

By the decision of the Assembly of Belgrade, GSP "Belgrade" in 1990 became a public utility company, founded by the city. In 1991, with a total of 1,393 vehicles, with average age of 4.5 years, the streets of Belgrade was at the peak was about 1,130 vehicles a day carrying about 2.5 million passengers. The crisis in the former Yugoslavia, which escalated in the second half of 1991, led to the introduction of economic sanctions by UN Security Council to Federal Republic of Yugoslavia, and the influx of a large number of displaced persons in Belgrade. Investments in the purchase of new vehicles, spare parts and maintenance of the infrastructure was minimal. During 1993, due to the inability of continuous maintenance of the public transport problems in the procurement of oil and tires, price growth, transport declined in the number of vehicles in traffic, so that at the end of the year only 400 vehicles were in operation. Some lines were eliminated or shortened. The function of public transport in Belgrade had been damaged.

During 1994 and 1995, the GSP managed to raise the level of transportation, revitalize the fleet to an average of 909 vehicles on weekdays. At the beginning of 1998, in public transport private transporters were included. Compared to the previous year, it had 127 vehicles less, along with a tendency of further decline. The unified tariff system ceased to existand passed on ticketing in vehicles by the conductor. After the start of NATO bombing of Yugoslavia on 24 March 1999, GSP "Beograd" transferred to work in the war environment, which meant the abolition or curtailment of a large number of lines. In the aftermath of the NATO bombing, the problem was lack of vehicles. The unfavorable situation continued in 2000. The outdated fleet, low technical condition of vehicles, lack of spare parts, frequent reduction of traffic due to fuel shortages are only part of the problem that led to the introduction of emergency measures by the Republic government. Significant changes have taken place after the events of October 2000, when the city's new government has opted for the revitalization of the GSP, as a holder of public transport system in Belgrade. A goal that was set before GSP "Belgrade" was to reach the level of the enterprise from the beginning of the 1990s. By the end of the year, most of former lines were reestablished.

In 2011, GSP Belgrade began with the acquisition of new Urbos 3 trams from the Spanish manufacturer CAF. By the end of 2012, it was planned to supply 30 trams of this model. The new trams are commonly referred to as Španac (Spaniard) by Belgrade's residents.

GSP Belgrade introduced BusPlus on 1 February 2012. BusPlus is an electronic payment method where commuters load fares on a thin plastic card.^[6] Also, the private carriers were introduced and integrated in tariff system – Integrated Tariff System (ITS).^[7] There are 145 lines, out of which 12 are tram, 8 are trolleybus and 125 are bus lines. Service operates daily between 4 am and midnight, with a limited night bus system. GSP also operates school bus lines, and transportation for the disabled. The entire traffic grid is divided in two zones.

As of 2017, GSP Belgrade has 1,582 vehicles in operation.^[8] Most of GSP's revenue is still generated through subsidies by the city of Belgrade; in 2017, that amount stood at 65 million euros.^[9]

In April 2019, GSP along with the city of Belgrade signed a contract to purchase 244 new buses, of which 70 are manufactured by Turkish BMC and 174 by Chinese Higer.^[10]

Until the beginning of the 1960s, the vehicles have been colored by cream and red color scheme (buses have been colored until 1961. trolleybuses and trams are colored until 1964). From the beginning of the 1960s, the vehicles have been colored by Mussolini livery – light and dark green color scheme (for buses from 1961 to 1967, for trolleybuses and trams from 1964 to 1970).

From the end of the 1960s, the vehicles have been colored by cream and green color scheme (for trams and trolleybuses from 1970 to 1979, for buses from 1967 to 1987). From the end of the 1970s, the vehicles have been colored by cream and red color scheme again (for trams and trolleybuses from 1979 to 2003, for buses from 1987 to 2004).

From the beginning of 2000s, the vehicles are coloring by three color schemes with blue bottom (trams are colored by red and blue color scheme from 2002, trolleybuses are colored by orange and blue color scheme from 2003 (for some units, but their current color scheme is red from 2010), and buses are colored by yellow and blue color scheme from 2004 (in future, their color scheme will be red from 2015)). Some vehicles have been colored by cream and blue color scheme (like the private buses in the end of the 1990s, for example: one trolleybus ZiU-9 and one tram ČKD-Tatra KT4YU have been colored in cream and blue color scheme in 1993 (in collaboration with Mašinska Industrija Niš - MIN), and two trams ČKD-Tatra KT4YU have been coloured in cream and blue colour scheme in 2001).