"With some very creditable and consistent results over the years, the team's current league position is unacceptable to everyone associated with the club and it was felt that a change was necessary at this point.
"The search for a replacement begins at once. The club would like to thank Simon sincerely for his hard work, commitment and honesty throughout his time at the Wizards and of course, wish him well in the future."
Yesterday's announcement ended King's association with the Wizards having spent seven years in charge. He led the Port Talbot club to a third-placed finish in 2009 and 2012 and to a runners-up place in the 2011 SWALEC Cup final.
This season though, the Wizards have struggled in the league and currently sit bottom of the Principality Premiership table.
King said: "The last couple of years haven't been the best but we still qualified for the British & Irish Cup.
"And if a couple of senior players hadn't got injured things might have been different.
"People outside the circle don't realise the problems we've had. We lost Will Price, Matthew Jenkins and David Pritchard to injury. They are big losses. I'm confident Aberavon will turn it around."
King added: "Of course I'll miss the club, seven years is a long time.
"But I'll dust myself down. I've been coaching since 1994 and I still think I've got something to offer. If I didn't I'd give up.
"It's difficult to have four clubs all from the same region, and if you look at how many games we've won, we've done better than the others.
"It's been a privilege to coach Aberavon and I've got nothing but admiration and respect for the people in charge there.
"It's disappointing but I've got broad shoulders."