“Elon fatigue” may have finally claimed the No. 2 executive at Tesla — and Wall Street is freaking out.

JB Straubel — a legendary Silicon Valley inventor who pioneered Tesla’s battery technology and helped Musk found the company 16 years ago — revealed he is leaving Tesla’s brutal daily grind in favor of a part-time consulting role.

News of Straubel’s departure came near the end of a late-Wednesday conference call as Tesla revealed a wider-than-expected loss and backed off a promise to turn a profit this year. The nasty surprise helped push Tesla shares down nearly 14% to $228.82, their worst day since 2013.

Musk, known for regularly sleeping on Tesla’s factory floor as he logs work weeks of 100 hours or more to meet production deadlines for the Model 3 sedan, on Thursday confirmed that 43-year-old Straubel played a “fundamental role in creating and building Tesla.”

“Tesla wouldn’t exist, basically,” if the pair hadn’t gone out to lunch in 2003, Musk said.

Straubel, for his part, insisted during the call with analysts that he will not be “disappearing” and that he loves Tesla and “always will.”

“I just wanted to make sure that people understand that this was not some, you know, lack of confidence in the company or the team or anything like that,” he said.

Straubel was responsible for the design of the original battery pack and motor that went into the first Tesla Roadster, and has steered the development of components for all of Tesla’s subsequent vehicles. He also developed programs like Tesla’s Supercharger network, as well as its energy business.

Straubel’s departure wasn’t the first high-profile exit at Tesla. In January, chief financial officer Deepak Ahuja announced his retirement at the end of an earnings call.

CFRA analyst Garrett Nelson told The Post that he doesn’t view Straubel’s departure as a result of a disagreement with the direction of the company.

“More than anything, it’s a reflection of fatigue,” Nelson said. “It’s similar to the fatigue that several other executive expressed prior to their departures.”

Musk — who famously bragged about working 120-hour weeks as Tesla was ramping up Model 3 production in 2018 — has long encouraged his employees to push themselves to reach company goals.

“There are way easier places to work, but nobody ever changed the world on 40 hours a week,” Musk tweeted in November of last year. In an interview with Recode the same month, Tesla’s billionaire CEO said that “everyone” at the company worked 100-hour weeks at times.

Still, the departure rattled Wall Street after Tesla delivered greater-than-expected losses and warned that it would putting the emphasis less on profit and more on volume growth, increasing production capacity and generating cash.

“Straubel has been at the forefront of the company’s technology leadership, which we believe will increasingly be called into question as competitors catch up,” Cowen analysts said.