The Gunners were crowned champions of Europe on Saturday night, upsetting the odds to stun favourites Barcelona and win 1-0.
Stina Blackstenius scored the second-half winner as Arsenal lifted the Champions League trophy for a second time. They remain the only English winners of the competition.
Thousands of fans gathered by the Emirates Stadium on Monday morning before the players and staff gathered on stage to address the crowd.
They took it in turns to lift the trophy, each time greeted with huge roars from those gathered below, while a playlist including Sweet Caroline and The Best blasted out.
England captain Williamson, who joined Arsenal at the age of nine, revealed she was adamant the club were going to win the Champions League after beating Lyon in the semi-finals.
“I've been saying the whole time,” Williamson said.
Arsenal's Katie McCabe and teammates with the trophy at the Emirates. Action Images via Reuters/Andrew Couldridge
Arsenal's Katie McCabe and teammates with the trophy at the Emirates. Action Images via Reuters/Andrew Couldridge
“All my team-mates will tell you, I said, 'Do you believe in magic?' That's what I could feel. I knew it was going to happen against Lyon, I knew it was going to happen in the final. And magic delivered.
"It's a difficult task to defend against Barcelona. It was a bit of an onslaught at time but we did good. We had a game plan and everyone delivered.
"My club. My Arsenal. Champions League winners. European champions. Let's go."
Katie McCabe also took the microphone and led the crowd in serenading club captain Kim Little, before adding: "I've been with these girls for 10 years. Red is in my blood. These group of girls is everything you need.”
Blackstenius was the hero for Arsenal in Lisbon, coming off the bench to deliver the winning goal and write her name in the club’s history books.
With Alessia Russo in fine form, the Swedish striker has had her opportunities limited at times this season, but she took her chance on the biggest stage.
"It's a huge game to play,” Blackstenius said. “I was quite nervous of course. We spoke about stretching them, it only takes one opportunity.
"It all went so quick. It was a really, really good pass. I just tried to hit the target. When I saw it was actually a goal I was a bit in shock at first. I'm just so happy."