Henry Leonard Campbell Brassey, 1st Baron Brassey of Apethorpe, DL, of Apethorpe Hall in Northamptonshire, was a British Conservative Party politician.

The 1903 Newmarket by-election was a parliamentary by-election held on 2 January 1903 to fill a vacancy in the United Kingdom House of Commons for the Eastern or Newmarket Division of Cambridgeshire.