While much is known about marine aerosol generation, little is known about aerosol produced from breaking waves in large freshwater environments or about what implications this aerosol may have for air quality and climate. We present here evidence of significant particle production from the surface of the Great Lakes. In 2009, vertical profiles of the submicron particle size distribution were measured over Lake Michigan, where we found substantial increases in ultrafine particle concentrations with the source at or near the lake surface. The Aitken mode aerosol concentration exhibits an exponential correlation with wind speed, suggesting that breaking waves along the surface were causing the observed particle formation. A calculated dry particle size distribution based on analysis of the lake water shows reasonable agreement with our observed size spectra. This new particle production source is previously un-studied and could significantly impact atmospheric composition in the region surrounding fresh water lakes.