Podillia (Подлля) is a historic region in Eastern Europe, located in the west-central and south-western parts of Ukraine and in northeastern Moldova (i.e. northern Transnistria). The name derives from Old Slavic po, meaning "by/next to/along" and dol, "valley."

The area is part of the vast East European Plain, confined by the Dnister River and the Carpathian arc in the southwest. It comprises an area of about 40,000 km2 (15,000 sq mi), extending for 320 km (200 mi) from northwest to southeast on the left bank of the Dnister. In the same direction run two ranges of relatively low hills separated by the Southern Buh.. The Podillian Upland, an elongated, up to 472 ft (144 m) high plateau stretches from the Western and Southern Buh rivers to the Dnister, includes hill countries and mountainous regions with canyon-like fluvial valleys.

Podiillia lies east of historic Red Ruthenia, i.e. the eastern half of Halychyna, beyond the Seret River, a tributary of the Dnister. In the northwest it borders on Volyn. It is made up of the present-day Ukrainian Vinnytsia Oblast and southern and central Khmelnytskyi Oblast. The Podillian lands further include parts of adjacent Ternopil Oblast in the west and Kyiv Oblast in the northeast. In the east it consists of the neighboring parts of Cherkasy, Kirovohrad and Odesa Oblasts, as well as the northern half of Transnistria.

Two large rivers, with numerous tributaries, drain the region: the Dnister, which forms its boundary with Moldova and is navigable throughout its length, and the Southern Buh, which flows almost parallel to the former in a higher, sometimes swampy, valley, interrupted in several places by rapids.

In Podillia, "black earth" (chornozem) soil predominates, making it a very fertile agricultural area. Marshes occur only beside the Buh.