Alekseyeva, who was born in Crimea in 1927, helped found the Moscow Helsinki Watch Group in 1976 and is one of the few Soviet-era dissidents who remains active now in Russia's rights movement.
She was among the activists to step down from Russia's presidential Human Rights Council in protest over Vladimir Putin's reelection as president this spring.
She has also been a vocal critic of new legislation proposing harsh restrictions on nongovernmental organizations, the Internet, and public protests.
In an interview with RFE/RL's Russian Service, fellow activist and former dissident Sergei Kovalyov praised Alekseyeva for her bravery and fight for what he called Russians' "right to self-esteem."
The Kremlin press service reports that Putin also offered his congratulations to Alekseyeva.
In a statement, he praised her for aiding the "development of dialogue between the government and the public" and said she had remained loyal throughout her lifetime to the "high ideals of service to society."