"In some cases, we'll provide direct funding to these organizations", Clinton wrote in an emailed message announcing Onward Together, which echoes her "Stronger together" presidential campaign slogan.
The former secretary of state was not expected to rejoin the Clinton Foundation, the primary focus of her husband and daughter.
On Monday she used Twitter to make the announcement, saying she had been spending the last few months 'reflecting, spending time with family-and, yes, taking walks in the woods'.
'I'm now back to being an activist citizen and part of the resistance, ' she said in New York City in early May.
That's about three million more than Trump.
The groups included Indivisible, a collection of former congressional staffers advising people on how to make their representatives listen to voices, and the Color of Change, which pushes for legal and voting reforms to end discrimination against African Americans.
In the email, Clinton praised political organization efforts such as the Women's March in January and credited them with paving a way forward for Democrats.
Clinton has maintained a low profile in 2017, considering the next step to follow on from her previous positions as secretary of state (2009-2013), U.S. senator from NY (2001-2009), and first lady (1993-2001).
Hillary Clinton, the 2016 Democratic presidential nominee, formally launched her political action group on Monday.
"This year hasn't been what I envisioned", Clinton wrote.
After suffering defeat at a 306 to 203 electoral vote count in favor of Trump, Clinton said she believes "more than ever" in her decades-long political career that "citizen engagement" is important for maintaining democracy.
With the tag line "Resist, insist, persist, enlist", Clinton has formed her version of a resistance group. I'm so inspired by everyone stepping up to organize and lead.
The group's mission statement does not reference Trump directly but takes an indirect swipe at the current president by noting Clinton won 66 million votes in the last election.
Onward Together also temporarily answers a key question for Clinton: What will you do next?