Right-back Kieran Trippier, replaced by semi-final starter Bukayo Saka, enters the squad, suggesting England will line up a five-a-side defense.
Southgate often went for a 4-3-3 system during the tournament but moved up to five in the back for the round of 16 with Germany.
Follow Euro 2020 preparations live as police warn fans
It was a risky move that initially raised some concern among commentators but paid off and earned the manager’s respect when England won with a 2-0 victory.
Former England manager Steve McClaren told Sky Sports News: “A courageous call from Gareth. I’ve only done it once in the tournament, against Germany, and it was a massive call. It worked, it must work again. “
“I think, why did he do that – Gareth is very pragmatic,” added McClaren.
“I’ve been saying it from the start, it’s about ‘how to win this game in 95 minutes, overtime, penalties’, and he knows he has to stay in the game, keep it tight. Clean sheets save you matches. ”
Former England goalkeeper David Seaman admitted he was “surprised” by England’s expected lineup for the Euro final tonight.
Seaman, a former England team-mate at Southgate, has said he believes the Three Lions boss will name an unchanged side after the semi-final victory over Denmark.
“He knows what he’s doing. Going with three behind, does that mean we’re going to be more offensive? asked the sailor.
“Hopefully we can attack the Italians behind the scenes, that’s where they’re a little vulnerable, and hopefully get some crosses against Harry Kane. “
Gareth Southgate a tell fans their “support and energy has given us a huge boost” as the team prepare to face Italy.
In a video message posted a few hours before kick-off at Wembley, south gate thanked the fans for their “incredible support”.
Tonight’s final between England and Italy will be the first time Wembley has hosted a major final since Euro 96, when Germany beat the Czech Republic in the final.
The previous occasion was at the 1966 World Cup, the last time England won a major international football tournament.
Thousands of England fans have started to gather outside Wembley Stadium as the team prepare to end 55 years of injuries and police are now urging anyone without a ticket not to attend.
Metropolitan Police said the Wembley area is “extremely busy” and officers “engage with the crowds and keep people safe”.