Outspoken activist short seller Andrew Left was convicted on securities fraud charges over manipulating stock prices — a surprise verdict that sent shock waves through Wall Street.

A jury in Los Angeles federal court found Left, 55, guilty on one securities-fraud scheme count and 12 securities-fraud counts late Monday.

The famed trader’s conviction left other short sellers wondering if they, too, are now vulnerable to market-manipulation charges.

“Amazing. I was actually criminally convicted on manipulating Nvidia Facebook and Tesla for telling the truth and making a profit. I am a bit speechless,” Left told DealBook.

“What this does for future of free speech is chilling. Can Individual investors not talk SpaceX? Wow. Still shocked,” he added.

The conviction marked a dramatic fall for the founder of Citron Research, whose reports once rattled Wall Street and sent targeted stocks tumbling.

Federal prosecutors said Left used his reputation and social-media following to move stock prices in his favor, publicly touting bullish or bearish views before quickly exiting trades once prices moved.

“The jury got it wrong,” Left told reporters outside court. “Obviously, this is not the end of the road for us.”

He said he plans to appeal.

The conviction culminated a years-long federal investigation into whether prominent short sellers used their public platforms to manipulate markets.

The feds said Left’s stock commentary was designed less to reflect genuine conviction than to trigger short-term price swings that generated profits for his own trading accounts.

Left earned roughly $20 million from the trades at issue in the case, according to the feds.

The Justice Department highlighted examples in which Left publicly promoted stocks or criticized companies, then rapidly closed out positions after shares moved in the desired direction.

He was convicted on counts involving trades on Nvidia, Tesla, Cronos Group, American Airlines and other companies.

The jury acquitted him on several counts tied to trades involving Beyond Meat, General Electric, Luckin Coffee and Namaste Technologies.

The feds did not accuse Left of saying anything false, but focused on how rapidly he closed out his positions after praising or blasting companies online.

“Andrew Left is an innocent man. Nobody lost a dollar because of his commentary. And the prosecution’s lead case agent admitted she could not point to one false statement in anything Andrew said about these stocks,” Left’s defense team told The Post in a statement.

“The prosecution’s theory is that truthful statements to the market can amount to fraud. That runs afoul of well-settled Supreme Court precedent, tramples the First Amendment, and will chill honest opinions about public companies.”

Left testified in his own defense during the three-week trial, insisting his market commentary reflected honest opinions and denying any effort to deceive investors.

He argued that he was simply an active trader and maintained that no rule required him to disclose every trade or how long he intended to hold a position.

Prior to the conviction, the market personality earned acclaim for high-profile calls against companies such as China Evergrande and Valeant Pharmaceuticals.

Several firms targeted by Citron later faced serious business or regulatory problems, bolstering Left’s reputation as one of Wall Street’s most feared short sellers.

Federal prosecutors, however, contended that even if some of his underlying views proved correct, investors were misled about his trading intentions and time horizon.

Left has framed the prosecution as an attack on financial commentary and market opinion, warning that the case could discourage investors from publicly sharing research while actively trading.

He faces sentencing on Aug. 31. The lead securities-fraud charge carries a maximum prison sentence of 25 years.

The Post has sought comment from Left.