Sizergh Castle is a stately home with garden and estate at Helsington in Cumbria, England, about 4 miles (6 km) south of Kendal. Located in historic Westmorland, the castle is a Grade I listed building. While remaining the home of the Hornyold-Strickland family, the castle with its garden and estate is in the care of the National Trust.

Strickland is an English toponymic surname derived from the manor of Strickland in the historical county of Westmorland, now Cumbria, England, represented geographically by the modern villages of Great Strickland and Little Strickland. The surname dates as far back as the 12th century in Westmorland, and is also found at an early date in the Scottish counties of Ayrshire and Lanarkshire.