Grybowski led developer Deepwater Wind as it installed the US' first offshore wind project off Rhode Island, which was completed in 2016.
He then joined Ørsted's US business when the Danish developer acquired Deepwater Wind in October 2018.
Ørsted said Grybowski's departure followed the completion of integration between the two companies.
"A decade ago, I started on this quest to establish a prominent place for offshore wind in America's energy future.
"Rhode Island provided the leadership with the first project, and I'm proud to say that offshore wind's time is now here," said Grybowski.
Following his departure, Grybowski will remain in Rhode Island investigating a start-up venture. He will also consult for Ørsted "for the time being".
A former corporate and regulatory lawyer from Rhode Island, Grybowski had deep political connections, which helped grease the wheels of Block Island. Grybowski also made sure to work with local stakeholders and workers on projects, something Ørsted is following suit with.
"Jeff is one of the pioneers of the offshore wind industry in the US, and his achievements are respected across the industry," said Thomas Brostrøm, president of Ørsted North America.
"He built an outstanding company at Deepwater Wind and we thank him for his contributions in helping Ørsted build the leading offshore wind platform in America. We wish him great success in the next phase of his journey," Brostrøm added.