Jesse Lingard, James Ward-Prowse and Ollie Watkins were also among the six names cut, but Trent Alexander-Arnold got the nod.
The Three Lions boss last week made the decision to name a provisional 33-man squad rather than his final 26-strong selection due to players’ injury concerns and continental cup final commitments.
Southgate has now finalised his Euro 2020 selection, trimming six players after Mason Greenwood withdrew through injury on the morning of the announcement.
Lingard, Ward-Prowse and Watkins missed out along with the uncapped trio of Ramsdale, York-born Ben Godfrey and former Leeds United loan defender Ben White.
Lingard’s outstanding start to life on loan from Manchester United at West Ham saw him brought in from the cold in March’s World Cup qualification triple-header.
The 28-year-old played a part in all three of those matches but Southgate indicated in the build-up that he was there due to the absence of the injured Jack Grealish and Jadon Sancho.
Southampton skipper Ward-Prowse played in two of those games and had been due to start the third until withdrawing through injury and has missed the cut, as he did for the 2019 Nations League finals.
Aston Villa striker Watkins scored on his debut against San Marino but was behind Harry Kane and Dominic Calvert-Lewin in the pecking order.
Alexander-Arnold was selected as one of four right-backs, joining Kieran Trippier, Reece James and Kyle Walker in the 26-man squad.
Southgate said on England’s YouTube channel: “I think every squad is difficult because we have a lot of talented players in this country.
“The most difficult thing is to not be able to take players who’ve been with us in previous matches and who are such good professionals.
“So, I know what a disappointment that is for them at the moment not to be going to a major championship.
“But we still have two friendlies to get to, and there’s been plenty of examples over the years where there have been injuries in those friendlies that have ruled people out.
“So there’s still time for those guys even though they’re not in at this moment in time.”
The England boss revealed Ramsdale, White and Godfrey were aware they were called up to be part of the squad for the two pre-tournament friendlies.
“You never want to give bad news,” he said of informing those who had not made the cut.
“It is lovely to give people debuts and bring people into the squad for the first time but it is much harder to deliver bad news.
“This time, there were three boys who new they were coming in for the experience of training with us and for these two matches and who knows what might happen and they have trained really well.”