Using data collected by the Voyager 1 and 2 spacecraft in 1980 and 1981, strong evidence is presented by a direct correlation between variations in the solar wind at Saturn and the level of activity of Saturn's nonthermal radio emission. Correlation coefficients of 57--58% are reached at lag times of 0-1 days between the arrival at Saturn of high pressure solar wind streams and the onset of increased radio emission. During both 160-day analysis intervals studied, the radio emission exhibits a long-term periodicity of 25 days, identical to the periodicity seen in the solar wind at this time and consistent with the solar rotation period. The energy coupling efficiency between the solar wind and the Saturn radio emission is estimated and compared with that for the earth.