MLTOMCAT is 42 years (1979-2020) of gap free ozone profile data sets that is created by correcting biases in a TOMCAT Chemical Transport Model (CTM) simulated ozone profiles. We use Random Forest regression model to correct model biases. Each file contain monthly mean zonal mean ozone profiles. There are 4 data files. MLTOMCAT_1979_2020_72_ht_vmr.nc contains ozone profiles on geometric height levels (1 to 60 km) in mixing ratio units, whereas MLTOMCAT_1979_2020_72_ht_nd.nc contains ozone profile in number density units. Similarly, MLTOMCAT_1979_2020_72_plev_vmr.nc contains ozone profiles on 43 MLS pressure levels (1000 to 0.1 hPa) in mixing ratio units, whereas MLTOMCAT_1979_2020_72_plev_nd.nc contains ozone profile in number density units. Please note that data below 300 hPa (~8km) and 1 hPa (~50 km) should be used with caution. A manuscript describing MLTOMCAT would be published in EESD (Dhomse et al., 2021)