The area that leads to the theatre’s second space is to take the name of the much-loved actress, broadcaster and author, who died aged 66 in October following a battle with cancer.
The motion was submitted by councillor Howard Mordue and seconded by councillor Janet Blake, and it was approved at a meeting of Aylesbury Vale District Council.
Mrs Bellingham, who grew up in Aston Abbotts, was a firm supporter of the theatre, taking part in the topping out ceremony in April 2009.
She also helped to launch the theatre’s first season in March 2010 and appeared on stage starring in Calendar Girls as part of the opening season.
Councillor Howard Mordue, cabinet member for leisure said: “This is an opportunity to honour Lynda Bellingham on behalf of the people of Aylesbury Vale.
“Her rich and varied career is an excellent example of what can be achieved through hard work and dedication.
“It seemed apt to name part of the theatre in her memory and we hope future actors and theatre groups will be inspired by her wonderful legacy.”
Elizabeth Adlington, chief executive of Aylesbury Waterside said: “Lynda’s support of Aylesbury Waterside Theatre makes this a fitting tribute to one of the entertainment industry’s most-loved names.
“I hope audiences will reflect fondly on the contribution Lynda made to theatre and entertainment when they visit The Waterside Theatre.
“We feel very privileged to have welcomed Lynda to the theatre on several occasions.”
Mrs Bellingham was born in Montreal in May 1948 after her father, an airline pilot, moved there for work, but grew up in Aston Abbotts and attended Aylesbury High School.
She was best known for starring in the Oxo adverts between 1983 and 1999 and for appearing on TV show Loose Women.
Mrs Bellingham was a high-profile supporter of Cancer Research UK and Macmillan Cancer Support and was honoured with an OBE for her charity work in 2014.