Actor-director Robert Redford is leaving Saturday for the Soviet Union for a 10-day trip to discuss two of his favorite subjects, films and the environment.

Redford was invited last December by Elem Klimov, president of the Soviet Filmmakers Union. Seven of his films will be shown in Leningrad, Moscow and Tbilisi.While in Moscow, Redford will be a co-host at discussion sessions on global environment and involving the Soviet Academy of Sciences, the University Corporation for Atmospheric Research, Boulder, Colo., and the Natural Resources Defense Council, New York.

The two-day meeting was initiated by the Institute for Resource Management, an organization created by Redford in 1981 that seeks solutions to environmental conflicts and controversies.

Soviet and American scientists and environmental-policy experts will discuss cooperation on the global warming some scientists believe is taking place due to ozone depletion in the upper atmosphere and the buildup of carbon dioxide.