The 35-year-old leader of the National Assembly, who declared himself interim leader of Venezuela earlier this year, defied a travel ban against him when he traveled to Colombia to attend a fundraising concert last month.
Guaido went on to visit several Latin American countries that support his campaign against Maduro, who was re-elected last year in a vote that the opposition and dozens of foreign nations say was invalid.
“Back in our loved country!” Guaido tweeted in Spanish after landing at the country’s main airport about 25 miles from Caracas. “Venezuela, we just went through immigration and they mobilized us to where our people await!”
He added: “We entered Venezuela as free citizens, nobody should say otherwise.”
Ahead of his return home, Guaido said the goal was to intensify internal pressure against Maduro, despite the possibility of being arrested for defying the travel ban.
In recent messages to his supporters, Guaido appealed for huge demonstrations coinciding with his arrival as a way to pressure Maduro to resign.
Workers set up a state in a Caracas plaza where demonstrators plan to gather, and protests were planned elsewhere in the country.
U.S. National Security Adviser John Bolton tweeted that threats or action by Maduro's government against Guaido "will be met with a strong and significant response from the United States and the international community."
The United States and about 50 other countries recognize Guaido as the rightful president of Venezuela, which is in the midst of a political and humanitarian crisis.
Several European ambassadors who support his campaign for a change of leadership in Venezuela were at the scene as he arrived Monday.
Meanwhile, Maduro, who has said he is the target of a U.S.-backed coup plot, has urged Venezuelans to enjoy the carnival season slated for Monday and Tuesday, even though many people don't have the resources to travel to beaches and other holiday spots.
The Associated Press contributed to this report.