More than 82,000 Moscow residents bathed in ice-cold lake- and riverwater overnight to mark the Epiphany.
A spokesman for the Emergency Ministry's Moscow branch said no health incidents were reported.
The air temperature in the Russian capital was around minus-13 degrees Celsius.
Many more Russians across the mainly Orthodox country celebrated the date -- marking the baptism of Jesus Christ by John the Baptist and the beginning of his ministry -- in similar fashion.
Epiphany is one of the Great Feasts.
The Russian Orthodox Church celebrates it on January 19 in line with the Julian calendar.
Honoring an old Russian tradition, cross-shaped holes are cut in ice over lakes and rivers and celebrators plunge into the water -- typically three times, in honor of the Holy Trinity -- around midnight, often after an attending priest says a prayer.
Based on reporting by ITAR-TASS and Ria-Novosti