Sal Brinton will take over from Tim Farron in January 2015.
A former group leader on Cambridgeshire County Council, Baroness Sal Brinton is currently the Lib Dem health spokeswoman in the Lords.
Sal Brinton also runs the party’s leadership programme, which supports candidates from under-represented groups, such as women and the disabled.
Sal Brinton said her first priority would be to move the party’s campaigning ability into “top gear” in preparation for next year’s general and local elections.
“My role will be to represent the members, and make the changes that they want happen” she added.