Investors reacted angrily on Monday to the poison pill Papa John’s board enacted over the weekend — pushing the stock of the pizza maker to its lowest level since February 2016.

Shares lost 9.8 percent in the session to close at $46.56. In the past month, the ­$1.5 billion Louisville, Ky., firm has lost ­$300 million in market cap.

The pizza chain’s founder and former chairman, John Schnatter, drew flak earlier this month after it was learned he used the N-word during a May media training session.

Schnatter acknowledged using the racial slur and apologized — but the company’s board pushed him earlier in July to give up his chairman’s post.

The board adopted the poison pill Sunday after Schnatter, who owns 29 percent of the chain, hinted that he might reach out to shareholders in an attempt to win control of the company — as part of an effort to regain his chairman’s role.

Under the poison pill, shareholders will receive the right to one preferred share for every share they own. The right will be triggered when someone buys a 15 percent stake in the company without the board’s OK.

Schnatter’s current stake is grandfathered in. The 56-year-old founder had been a highly visible spokesman for the 5,212-store chain — appearing in TV commercials and even in the company’s logo.

A special committee of the board decided to remove Schnatter’s likeness from the logo — and barred him from talking to the media.

It also voided an agreement it had with the founder that allowed him to use space at the company’s headquarters for offices and hinted that it wanted him to step down from the board.

Schnatter, who has lawyered up, feels the move to evict him was improper.

With both sides staking out their territory, the battle may become more heated before it’s resolved.