Cardigan Castle is a castle overlooking the River Teifi in Cardigan, Ceredigion, Wales. It is a Grade I listed building. The castle dates from the late 11th-century, though was rebuilt in 1244. Castle Green House was built inside the castle walls in the early 1800s. After falling into disrepair the castle was restored in the early 2000s and opened to the public in 2015. It is owned by Ceredigion County Council and now includes a heritage centre and open-air concert facilities. The castle's gardens are listed on the Cadw/ICOMOS Register of Parks and Gardens of Special Historic Interest in Wales.

The River Teifi in Wales forms the boundary for most of its length between the counties of Ceredigion and Carmarthenshire, and for the final 3 miles (4.8 km) of its total length of 76 miles (122 km), the boundary between Ceredigion and Pembrokeshire. Its estuary is northwest of Cardigan, known in Welsh as Aberteifi, meaning 'mouth of the Teifi'. Teifi has formerly been anglicised as "Tivy".