A Russian man pleaded guilty on Monday to taking part in a global, multiyear hacking operation that involved cyberattacks on a dozen American companies and an elaborate scheme to use stolen information to manipulate stocks and run illegal online-gambling businesses.

The man, Andrei Tyurin, 35, of Moscow, is the first person to be convicted in the case, which prosecutors have called one of the largest hacking cases ever uncovered. The information of more than 100 million customers was compromised, including the breach of 83 million customer accounts at JPMorgan Chase in 2014.

Charges against three other men — including Gery Shalon, a man prosecutors said orchestrated the criminal enterprise — are pending.

Mr. Tyurin pleaded guilty in United States District Court in Manhattan to six felony counts, including wire fraud, bank fraud and conspiracy to commit computer hacking.