Swainby is a village in the county of North Yorkshire, England. It is situated on the A172 road, 8 miles (13 km) north-east from Northallerton and 5 miles (8 km) south-west from the small market town of Stokesley.

Swainby is located at the north-western corner of the North York Moors National Park. The characteristics of the village and the surrounding area consist of traditional Yorkshire dry stone walls, hills, sheep, heather and moorland. The name of the village derives from Old Norse, Sveins and by which means the village next to the swans or the land of Svein's people.

The village is close to the ruins of Whorlton Castle; Swainby appears to have been built after its abandonment, possibly due to the Black Death (or some other disease) leaving the inhabitants of the castle low in number in 1428.

Holy Cross Church (Church of England) was designed by T. H. Wyatt; he was commissioned to do it by the Marquess of Ailesbury. It is in the Early English style and constructed of locally quarried stone. The grade II listed church was consecrated on 4 October 1877.

In the 19th century the housing of miners who worked the nearby hills for ironstone and jet led to an expansion of the village.

Scugdale Beck, a tributary of the River Leven, cuts northwards through the village with two roads either side of the water and houses built on both sides.

Swainby contains two public houses, "The Blacksmiths Arms" and "The Black Horse", and a caravan park with farm house.

Swainby is in Whorlton civil parish, the village is presently larger than the parish's namesake therefore the electoral ward is under Swainby's name. The ward's population was 1,820 at the 2011 census.