Mystery surrounds his departure, with Jon Shaw placed in interim charge until further noticed after he was “relieved of his duties”.
It comes after Darlington parted company with Josh Gowling on Boxing Day, before South Shields axed Julio Arch on Thursday.
Spennymoor Town are still without a permanent manager following following Jamie Chandler’s exit earlier in the season.
A Blyth Spartans statement read: “The club can announce that Graham Fenton has been relieved of his managerial duties and placed on gardening leave.
“Blyth Spartans would like to express their gratitude for the work in which Graham has done at Croft Park since being appointed as first-team manager in August 2022.
“He guided the club to preserve Step 2, National League North, status during the 2022/23 season and has played an instrumental role in the development of the youth set-up via Tyne Metropolitan College too, taking full charge of the under-19s at the beginning of this current campaign.
“From making 131 appearances and scoring 18 goals, having a brief spell as caretaker manager back in 2004, to being in charge for the past 16 months, his contributions across the whole club are hugely appreciated.
“In the interim, Jon Shaw will take full charge of the first-team. Further information and announcements will follow in due course.”