The mayoral ceremony took place in the council chamber earlier on Tuesday and Councilor Gavan takes over from Richard Jones, who was deselected by the Labour party earlier this year and later joined the Liberal Democrats.
Councillor Gavan is the second openly gay mayor in succession in Sandwell and his consort is his husband Adam Kennedy, while his deputy is Councillor Elaine Giles of Newton ward.
At the ceremony, votes of thanks were passed to the outgoing mayor and deputy mayor.
The new mayor confirmed he will be raising money for dementia in Sandwell by supporting Age UK and BUDS (Better Understanding of Dementia for Sandwell).
He said: "I am privileged and humbled to be elected by my councillor colleagues as mayor.
"It has been a long journey to get here and 47 years ago I was able to kick the addictions of alcohol and drugs with the continuous help of AA.
"In 1997 I was founder chair of Birmingham Pride and in 2018 I was cabinet member responsible for the Sandwell Aquatics Centre, built on time, on budget and host to the Commonwealth Games.
"I have so many people to thank. Firstly I would like to thank the outgoing mayoral team for all their hard work over the last year.
"I would also like to thank my local MP, The Right Honourable Mr John Spellar for his continued support over the years, my AA friends world-wide, and the class of Birmingham Pride 1997 to whom I wish all the best for the biggest and best Pride ever in 2023.
"I also want to wish every success to the leader, Councillor Kerrie Carmichael, her cabinet and all councillors new and old across the chamber whatever their political allegiance."
The Mayor is the first citizen of Sandwell and whilst the role is non-political, they preside over meetings of the council and attend events across the borough, also representing it at functions outside of it.