Viscount Mersey, of Toxteth in the County Palatine of Lancaster, is a title in the Peerage of the United Kingdom.

It was created in 1916 for the lawyer and politician John Bigham, 1st Baron Mersey.

He had already been created Baron Mersey, of Toxteth in the County Palatine of Lancaster, in 1910, also in the Peerage of the United Kingdom.

They were both succeeded by their son, the fourth Viscount Mersey and thirteenth Lord Nairne.

The heir presumptive (to the Mersey but not Nairne titles) is the present holder's cousin Charles Richard Petty Bigham (b.