A modular subsea converter for providing a frequency conversion of AC electric power is provided. The modular subsea converter includes at least one base module having a subsea enclosure and electrical connections disposed within the subsea enclosure. It further includes at least one converter module having a converter unit. The converter module is coupled to the base module and has a subsea enclosure in which the converter unit is disposed. The electrical connections of the base module are coupled to the converter unit of the converter module and the subsea enclosure of the converter module is mounted to the subsea enclosure of the base module.