The defender will lead the side out on Saturday
The skipper, from Newport Pagnell, was mascot for the Gunners when the side last made 18 years ago, but will lead them out at the Jose Alvalade Stadium in Lisbon - home of Sporting Lisbon.
They will have their work cut out for them though. Barcelona crushed fellow Londoners Chelsea in the semi-finals 8-2 on aggregate as they seek out a third consecutive Champions League crown.
Despite being the underdogs heading into the game, Williamson hopes that moniker will actually play into their hands.
Leah Williamson (sixth from the left) before the Womens UEFA Cup Final 2nd leg Between Arsenal Women and Umea on April 29, 2007Leah Williamson (sixth from the left) before the Womens UEFA Cup Final 2nd leg Between Arsenal Women and Umea on April 29, 2007
Leah Williamson (sixth from the left) before the Womens UEFA Cup Final 2nd leg Between Arsenal Women and Umea on April 29, 2007 | Arsenal FC via Getty Images
"On paper I'm not surprised because it would be disrespectful to think any other way given what they have achieved in the last three years in the competition," she said.
"When we speak of Barcelona, everyone is very respectful and humble to what they are as a football club and what they have achieved. We are going there to win. It's not an underdog mentality in that sense.
"Now the trophy is on offer and we have one game to go and do it. We go there with the belief we will do it."
The England Lionesses captain continued: "Recently our English teams have done really well and got further and further, but to bring those nights and bring that success back to England would be an incredible achievement seeing as it has been so long.
"I'm very proud to play for a club that has such a rich history. As a player, when you are the person that walks out on to the pitch, you are responsible for the legacy that lives on past you behind the badge.
"We want to be involved and we want to commit. We want to be part of that history and bring more success to the club and the name and what it deserves."
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