No. 1 Fighter Sector (1FS) was a Royal Australian Air Force (RAAF) unit formed at Bankstown, New South Wales on 25 February 1942.
The RAAF commandeered Capitol Theatre at Bankstown for use as an operations and plotting facility on 14 March 1942.
No. 1 Fighter Sector handed over operations to United States Army Air Corps (USAAC) on 10 April 1942. The operations shifted to a disused railway tunnel at St James railway station in Sydney.
On 13 August 1942, the RAAF resumed operations of No. 1 Fighter Sector and on 7 September 1942 the unit moved back to Bankstown. No. 1 Fighter Sector was renamed No. 101 Fighter Sector (101FS) on 18 October 1943 and was further renamed No. 101 Fighter Control Unit (101FCU) on 7 March 1944.
Unit became Air Defence Headquarters Sydney (ADHQ) on 21 January 1945 and moved into a three storey semi-underground purpose built operations and plotting facility at Bankstown.
ADHQ was disbanded on 27 January 1947.
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