The 25-year-old had proved to be hit with the Stark’s Park faithful during his two seasons in Kirkcaldy where he was an almost ever present, making 85 appearances in total and scoring four goals.
He decided to move on after his contract with Raith had expired.
He tweeted: “Thanks to the Raith fans for kind messages and amazing support over the past two years!
"Thanks also to my team mates, proud of what we all achieved.
"Sat nights wont be the same, wish the main man Jim and everyone at the club all the best.”
New boss Hartley, who played for Raith in the late 1990s, said: “Reghan is someone I've worked with before.
"A great character and hungry for success.
"He can play in multiple positions which gives us great options.
"He works hard and we are looking forward to getting him involved with a busy few weeks of pre-season to come.”
Tumilty said: “I’m delighted to sign for Hartlepool United.
"This is a great opportunity to play in the EFL and also work with Paul once again.
"When I was aware of the interest, there was only one club I wanted to sign for.
"I have seen videos and photos of how great these fans can be and I can't wait to get started'.