A spokesman for the agency confirmed the resignation but declined to comment further.
Lee was nominated by President Barack Obama and confirmed to the role in March 2015. A former Google executive who advocated strongly for women and minorities, Lee took the helm of the patent office at a crucial time for the technology industry. Tech companies were awash in frivolous lawsuits, many involving software patents, filed by "patent trolls" — companies that control intellectual property but derive much of their income from legal action rather than the manufacture of goods.
Much of this litigation, analysts said, stemmed from low-quality patents that should not have been approved in the first place. While in office, Lee oversaw and defended the agency's practice of invalidating low-quality patents that were brought to its attention. The agency published a report in August 2015 showing that the process had resulted in roughly 1 in 4 questionable patents being overturned.
Although Lee served through the end of Obama's tenure, her status came into question after President Trump was sworn in. For weeks, the patent office declined to say whether Lee was still its director, despite the fact that she had appeared to bid staff goodbye at an event in January.
Current and former staffers at the agency told The Post then that Lee was continuing to perform some of her office's functions, even though a website for the Commerce Department listed the director's position as unfilled.
It was not until early March that the patent office clarified that Lee was indeed continuing as director, sending a letter to University of Missouri law professor Dennis Crouch to confirm her role.
Now, Lee's sudden departure adds to the list of vacancies that Trump will be expected to fill, leaving businesses and inventors wondering what — and who — will come next.
The White House didn't immediately respond to a request for comment.
It is not clear what Lee will do next. But in a post on her Facebook page, she said she looked forward to the future.
“It has been a special honor,” she wrote, “to be the first woman to hold the position of Under Secretary and Director of the USPTO in our country’s 200+ year history.”