The arrest came early on Monday just before a mass nationwide protest against corruption that has ended with hundreds of demonstrators taken into police custody.
Navalny was taken by the police from the entrance of his home on Monday in central Moscow, his wife wrote on his Twitter account, posting a photo of him getting into a police car.
"Hello. This is Yulia Navalnaya ... Alexei has been detained in the stairwell," she wrote about a half-hour before the demonstration was to begin.
The protest will still go ahead, she added.
Electricity in Navalny's office was also cut off, Navalnaya's spokeswoman told her 33,000 followers on Twitter.
Navalny had called on his supporters to mark the Russia Day holiday on Monday with protests against what he called a corrupt system of rule overseen by Russian President Vladimir Putin.
Authorities in Moscow had agreed to a location away from the city centre, but Navalny called for the protest to be moved to Tverskaya Street, one of the city's main thoroughfares, citing interference in building a stage for speakers at the agreed-upon venue.
After the change, Moscow police warned that "any provocative actions from the protesters' side will be considered a threat to public order and will be immediately suppressed".
A Russian NGO tracking arrests said more than 200 people had been detained in Moscow and St Petersburg in the morning.
"About 121 people were detained in Moscow up to this point. In Saint-Petersburg - 137," the OVD-Info group, which operates a detention hotline, wrote on Twitter.
But the arrests continued throughout the day.
In St Petersburg, an Associated Press reporter counted about 500 people forced into police buses.
Navalny's website reported on Monday that protests were held in more than half a dozen cities in the Far East, including the major Pacific ports of Vladivostok and Khabarovsk and in Siberia's Barnaul.
Photos on the website suggested turnouts of hundreds at the rallies.
More than 1,000 protesters were arrested at a similar rally on March 26.
The protests in March took place in scores of cities across the country, the largest show of discontent in years. Navalny was jailed for 15 days after those protests.
The 41-year-old lawyer has announced his candidacy for the presidential election in 2018.
Navalny, a staunch Kremlin critic and anti-corruption campaigner, has long been the most visible opposition figure to Putin’s rule. In April, he suffered damage to one eye after an attacker doused his face with a green antiseptic liquid.
Author: News agencies