The 39-year-old, who has played over 500 competitive games in his career, has joined the Holy Blues from NPL Premier League rivals Scarborough Athletic.
Trinity manager Tom Shaw said: “We are looking to put together a young, hungry and energetic side, but to complement that, we also need to recruit an experienced spine - a core group of good professionals - and Neal certainly offers that.
“He is a vastly experienced player and that knowledge and nous will be invaluable to the group of players we are excited about putting together.”
After nearly 150 league outings for Notts County and Scunthorpe United, Bishop brought the curtain down on his EFL career having made nearly 80 league appearances in a two-year spell at Mansfield and worn the captain's armband at various clubs during his 23-year playing career.
Shaw also revealed that Bishop will combine his playing role with a coaching element, providing him with more valuable experience within the backroom set-up.
“Coaching will be a natural progression in the game for Neal, but at the moment he certainly has a desire and passion to continue to perform well on the pitch,” he said.
“He is as fit as they come and the outstanding reputation he has within the professional game speaks volumes about his character.
“I am really excited about Neal’s contribution to Gainsborough Trinity both on and off the pitch.”
Bishop said: “After speaking to Tom, the opportunity was too good to miss.
“I am passionate about playing and coaching and the chance to combine both is brilliant. I'm really looking forward to getting started, even though it's only May. It's a very exciting time to be involved with Gainsborough.”
Jovon Makama, 17, will join Trinity on loan next season after signing his first professional contract with Lincoln City.
Mean while 18-year-old Gianluca Bucci has returned to the club. The youngster, who played under Shaw at Lincoln’s academy, was at Frickley Athletic last season, where he played three times in a curtailed season.