Elon Musk on Wednesday unloaded more Tesla Inc. stock, bringing the total value of his share sales to more than $15 billion since the billionaire last month began a string of such transactions.

The sales came as Mr. Musk exercised more than 2.1 million Tesla stock options, according to regulatory filings late Wednesday. He sold more than 934,000 of the shares in the company he runs, valued at around $928.6 million, to cover tax withholdings, the disclosures state.

The...

Elon Musk on Wednesday unloaded more Tesla Inc. stock, bringing the total value of his share sales to more than $15 billion since the billionaire last month began a string of such transactions.

The sales came as Mr. Musk exercised more than 2.1 million Tesla stock options, according to regulatory filings late Wednesday. He sold more than 934,000 of the shares in the company he runs, valued at around $928.6 million, to cover tax withholdings, the disclosures state.

The latest transactions are part of a plan Mr. Musk set on Sept. 14 to exercise options and sell shares. The options he’s exercised are part of a tranche of around 23 million vested stock options set to expire in August 2022. He has exercised about 21.3 million of those options.

Mr. Musk said Wednesday on Twitter before the filings became public, “There are still a few tranches left, but almost done.”

After setting the stock plan, Mr. Musk last month polled Twitter users about whether he should sell 10% of his Tesla stock; those who voted on the social-media platform endorsed the idea. The chief executive began exercising Tesla stock options and selling shares in the company on Nov. 8.

Mr. Musk held around 170.5 million Tesla shares when he posted the Twitter poll and pledged to sell 10% of those holdings. He has sold around 14.8 million shares so far, leaving him at least a little more than $2 million in stock sales short to meet his commitment. The precise number depends on how he defines his ownership stake.

Exercising Tesla stock options has netted Mr. Musk more shares than he held at the time of the Twitter poll. His Tesla stock holdings now top 177 million shares.

Mr. Musk has a net worth of around $261 billion, making him the richest person on the Bloomberg Billionaires Index. He also has sold some stock over recent weeks not related to the stock options.

Tesla’s shares slumped after Mr. Musk began his selling last month. The stock, which closed up 7.49% on Wednesday at $1,008.87, is down more than 17% from the day Mr. Musk took the Twitter poll.

The Tesla CEO railed against a Biden Administration spending bill, including subsidies aimed at supporting the adoption of electric vehicles. The Wall Street Journal Interactive Edition

Write to Meghan Bobrowsky at Meghan.Bobrowsky@wsj.com