The 22-year-old moved to St James' Park in the summer of 2014, as part of a double deal that saw goalkeeper Karl Darlow join him on Tyneside.
Darlow and Lascelles were both loaned back to the City Ground for the duration of the season, before departing the banks of the Trent and going on to play pivotal roles for Newcastle last season.
Lascelles made quite an impression in the black and white stripes last term, despite United's relegation to the Championship, playing 21 times and netting twice.
He was made captain for the first time during a 6-0 win over Bohemians in pre-season, with the Derby-born man saying after the game: "It took my breath away because it's such a big thing for me."
Following his appointment as captain ahead of Newcastle's Championship opener at Fulham on Friday night, Lascelles couldn't hide his delight.
"It's an unbelievable feeling for a manager like Rafa Benitez to give me the captain's armband at a club like this," he said.
The defender continued: "It is a lot of responsibility for a young player but I will always give my all because I want what is best for the team and the club.
"It is such a proud moment for me and the biggest in my career so far.
"It is nice for someone to show that much trust in you, and I want to repay the manager's faith by leading this team back into the Premier League."
Lascelles's Spanish boss Benitez was pleased to give the youngster the responsibility, having previously said he has a captain's mentality.
Speaking to the club website, Benitez added: "We have a few players now in the squad who have the character to be captain, but Jamaal has proven himself to be a leader and a big personality in the dressing room and on the pitch.
"At the end of last season he really developed as a character and a man.
"I am pleased that Jamaal will be our captain, but I have also said to other players that they must too show their character, strength and leadership qualities to support the team."
Lascelles and Darlow will make their first return to the City Ground in league action when the Magpies face Forest on December 3, before the two teams meet again in the north east on New Year's Eve.