A Leader of the Council is a term used to describe the leader of the largest political group on a local government

Local government

Local government refers collectively to administrative authorities over areas that are smaller than a state.The term is used to contrast with offices at nation-state level, which are referred to as the central government, national government, or federal government...

 council.

England

In local government in England following the Local Government Act 2000

Local Government Act 2000

The Local Government Act 2000 is an Act of the Parliament of the United Kingdom that reformed local government in England and Wales. Its principal purposes are:...

 the position of Leader of the Council is used in Cabinet-style council

Cabinet-style council

A Cabinet-style Council is a type of local government which has been introduced in the United Kingdom for Local Councils following the introduction of the Local Government Act 2000....

s as an executive position chairing a cabinet.

Scotland

In local government in Scotland the Leader of the Council is elected as the leader of the largest political grouping of councillors in a local authority. The Leader of the Council has no executive or administrative powers designated by statute, but the position is salaried.