The main water resource in the territory of Plovdiv Municipality is the Maritsa River. It is defined as the largest river in the country and on the Balkan Peninsula after the Danube river with a drainage area of about 53 000 sq.km, and to the state border between Bulgaria and Greece - 21 992 sq.km, and with total length 524,6 km. It is also the deepest river in Bulgaria. It originates from the Rila Mountains, from the two Marichini lakes below Mancho Peak. The fertile lands and the important transport corridor that the river valley provides have been a prerequisite for the formation of many settlements alongside since Ancient times. For centuries it has connected Thrace with the Aegean Sea. It was navigable until the second half of the 19th century. Currently, there are a total of 51 settlements along the river in the three countries, of which: in Bulgaria (12 cities and 21 villages); in Greece (2 towns and 6 villages); in Turkey (3 cities and 7 villages). The length of the Maritsa River on the territory of Plovdiv Municipality is about 12 719 m.

The territorial scope of the Municipality of Plovdiv includes parts of four protected areas and one protected site around the Maritsa River.

Areas around the banks of the Maritsa River have been reconstructed and landscaped, which contributes to the use of the city's only water resource as a place for recreation.