Marconi Electronic Systems (MES), or GEC-Marconi as it was until 1998, was the defence arm of General Electric Company (GEC). It was demerged from GEC and bought by British Aerospace (BAe) on 30 November 1999 to form BAE Systems. GEC then renamed itself Marconi plc.

The General Electric Company (GEC) was a major British industrial conglomerate involved in consumer and defence electronics, communications, and engineering.