Tadcaster is a market town in North Yorkshire, England, lying on the Great North Road approximately 15 miles east of Leeds and 10 miles west of York. It is the last town on the River Wharfe before it joins the River Ouse about 10 miles downstream. It is part of the shire county of North Yorkshire, despite being further south than York, the traditional centre of Yorkshire and thus historically in the West Riding. Yet postal codes list it as being in Leeds and, as such, part of West Yorkshire.

The town is twinned with Saint Chély d'Apcher in France.