Sandanski–Petrich Valley (Bulgarian: Санданско-Петричка котловина, romanized: Sandansko-Petrichka kotlovina) is situated in southwestern Bulgaria along the river Struma and its right tributary Strumeshnitsa, with a very small part of the territory extending to Greece.

Due to the proximity to the Aegean Sea, the climate is continental Mediterranean, making Sandanski–Petrich Valley one of the warmest regions of Bulgaria.

The mild climate, numerous mineral springs and the abundance of natural and cultural landmarks within the valley and in its proximity favour agriculture, tourism and related industries.

Sandanski–Petrich Valley has a strategic location at the border with Greece and the Republic of North Macedonia and lies on the shortest route between the capital Sofia and the Mediterranean Sea.

The valley is located between the mountain ranges of Pirin to the east, Maleshevo and Ograzhden to the west and northwest, Belasitsa to the southwest, Sengelska and Slavyanka to the southeast.

Numerous mineral springs gush along the surrounding faults, along which the valley has sunk — near Sandanski, Levunovo, Marikostinovo, Rupite and Petrich.

[1] Although most of the valley's territory is arable land under intensive cultivation, it is nonetheless an important biodiversity hotspot in Bulgaria due to the strong Mediterranean influence.

[2] Sandanski–Petrich Valley is the only place of Bulgaria where plant species such as dragon lily (Dracunculus vulgaris)[3] or wild almond (Prunus webbii) may be found.

[2] The avifauna includes numerous nesting species, and in addition the valley is situated on one of the most important bird migration routes in the country.

[7] The mild Mediterranean climate of the Sandanski–Petrich Valley favours intensive agriculture, with orchards, vineyard, vegetable gardens and greenhouses.