Steyer, who at one time was thought to be eyeing a White House bid himself, says he will not be running for president in 2020.
Speaking at a press conference in Des Moines, the Democratic activist said he will focus on his "Need to Impeach" effort. He has already begun airing television ads that tout his Need to Impeach website.
It will include town halls across the country, a summit in Washington D.C. and mobilizing supporters around the nation.
Steyer, who made his wealth as a hedge fund manager, is also going to focus spending efforts on districts of House Democrats who chair key committees that would be involved in investigations and an impeachment of the president, as well as states that have Republican senators up for re-election in 2020.
"This is the biggest issue in American politics today," Steyer said. "We have a lawless president in the White House who is eroding our democracy and it is only going to get worse. Donald Trump's removal from power ultimately decides whether or not we can tackle every other challenge we face in America - and whether or not we continue to live in a democracy of, for, and by the people."
Steyer initially launched Need to Impeach in October 2017 with a $40 million investment and last year committed another $10 million. The group claims to have some 7 million supporters.
The group's impeachment summit in Washington is planned for late January.
You can watch his full statement here: