The Middlesbrough defender has been training with the Three Lions all week, despite not being named in Southgate’s initial squad after suffering an early-season injury with his club.
He had been one of England’s stand-out players in the Toulon Tournament earlier this summer, which was his first call-up since being involved with the U17s in 2010.
Gibson's form with Middlesbrough earned him an England Under-21s call-up
And after coming through all of the training sessions at St. George’s Park with the squad since Monday, he has now been added to the group who will head to Lithuania on Thursday morning for the first of two Euro qualifiers.
"It was a great boost to come along, after picking up an injury in the first game of the season," said Gibson, as the squad prepared for their flight to Kaunas.
"I tore my hamstring so to come back this quickly and be back involved in the England set up already, following my experiences from the summer, is brilliant.
"I couldn’t speak highly enough of the summer, I loved every minute of it, just spending time with the staff and the players and getting to know everyone.
"Just being a part of an England squad is an amazingly proud moment for me and my family and it’s something that I just want more of."
Gibson is a relative latecomer to the Under-21s campaign, as this week’s games are the final two in the qualifying group before the crucial play-offs take place in October.
With competition for places in Southgate’s squad proving high, everyone in the current group knows they are potentially playing for a spot in his next selection with the play-off draw being made on Friday 12 September, just four days after next week's game with Moldova.
"The gaffer will pick his best eleven for those games and it’s vitally important that we win these two and it’s a chance for all of the lads to shine in training and for those who are selected," he added.
“There’s a lot of competition for places, we’ve got a big squad even without the lads who aren’t here.”
Ben Gibson
"They will be hard games and obviously we’re going there to win them as a group and it will be a good experience and test for us.
"There’s a lot of competition for places, we’ve got a big squad even without the lads who aren’t here so we’ll be trying to shine and make sure we’re in that team come the play-offs.
"I had the experience of going away in the summer and that was a good test for us against different teams and hopefully that will benefit us in these next few games.”
It all comes on the back of such an unfortunate start to the season for the 21-year-old, who picked up his aforementioned injury just seconds into Boro’s first game of the season last month.
But after a full rehabilitation at the Riverside Stadium and a return to training with the Championship club last week, he’s now looking to go back to the north-east in even better condition after training and possibly playing for England over the next five days.
"Middlesbrough is obviously my bread and butter so the main thing is that I go back there and start playing again and if you want to play for your country, that’s a must," he admits.
"If you’re not playing for your club, you won’t play for England so it will be good to go back and hopefully get my place back after my injury and see how the season progresses from there."
The squad will train at the Daiaus ir Gireno Stadium in Kaunas after their arrival on Thursday afternoon, ahead of the game with Lithuania which kicks-off at 5pm (BST) on Friday.
