Huge boost for Falcons ahead of new season
The deals ensure two of Newcastle's most consistent homegrown performers will remain on Tyneside until at least the end of the 2019/20 season.
Director of Rugby Dean Richards delighted to have retained the duo.
"It is a massive endorsement of what we are doing that two of our top players have chosen to commit for this length of time, and Will and Mark typify everything we are about as a club.
"They are from our area, they have a tremendous work ethic and they have got to where they are in the game through sheer determination. Both of them are respected right around the Premiership as consistent top-quality players and I am sure our supporters share our delight at the fact they will be with us for the long term."
Wilson, the 26-year-old Cumbrian who was the top tackler in last season's Premiership, put pen to paper in the same month he married long-time partner, Amy.
The academy graduate said: "I had a good chat with Dean Richards and our Chairman Semore Kurdi. They expressed their ambition for the Falcons and I genuinely feel like this is my home, so I want to carry on here and help the club to keep improving.
"I have been here for a long time so I am in a good position to say how far the club has already come. I feel valued here, I am playing rugby with my best mates and every single person here shares the same determination to climb the Premiership table.
"It has been a class few weeks, all things considered. It has been hard to take it all in but I am incredibly happy on both a personal and professional level with how things are set. I am spending my future married to Amy and as a Newcastle Falcons player – everything is sorted and it is a great feeling."
On Welch, he added: "As well as my own contract I am absolutely delighted that Will has also signed for another four years.
"You always want to play with the best players and he definitely fits into that category. We started at the club at roughly the same time, we have played a lot of games together and we complement each other. He is a fantastic leader, he embodies what this club is about and we can really build something under his captaincy."
Welch became the Falcons' youngest ever captain when he assumed the leadership role aged 22 back in 2012, skippering the club to the RFU Championship title in his first season at the helm.
Making his first team debut for the club at the age of 17 while studying for his A-Levels at Royal Grammar School Newcastle, the 26-year-old flank already has 110 Premiership appearances under his belt after rising through the Falcons' academy.
Making 226 tackles in Premiership games last season, the third-highest in the division, he said: "Newcastle Falcons are my home town club. I supported them as a kid, I always wanted to play for the Falcons and I just want to help them be as successful as they can be.
"In order for that to happen we need the likes of Mark Wilson to be staying, and it is great that he will be here for the long term. We were both probably in similar situations when it came to making the decision, but I always knew I would beat myself up if I moved on and the Falcons were successful without me. I love Newcastle, I want to be here and I enjoy the challenge of trying to push us up the league table."
Welch added: "I also think it's important for our supporters to know that guys are prepared to stay when they have come through the academy here and made good progress in the first team.
"That hasn't always been the case in the past, we have had to cope with guys moving on but it is a sign of where things are going that people want to stay here on a longer-term basis. The team will benefit from that consistency of personnel, and when you look at the clubs who have done well in the game it is generally the ones who can retain their core group over a number of years who succeed."
