For decades the chancellor has followed the work and life of Solzhenitsyn, who passed away late on Sunday in Moscow, and "learned of his death with great sadness," her spokesman Thomas Steg told a news conference.
Merkel, who grew up in communist East Germany, has written to Russian President Dmitry Medvedev to express her condolences, Steg added.
Solzhenitsyn was a "great and important writer ... who through his work played a decisive role in bringing down the communist totalitarian system," Steg said.
The author won the Nobel Prize for literature in 1970 after depicting Soviet labour camps in harrowing detail. Beginning in 1945, he spent eight years in such camps.
He toiled obsessively to unearth the darkest secrets of Stalinist rule and his work ultimately dealt a crippling blow to the Soviet Union's authority.
He was eventually expelled in 1974 for his anti-Soviet views.