Sir Francis Brooks "Bob" Purchas, PC (19 June 1919 – 9 September 2003) was a British judge who sat on the Court of Appeal.
He later served at the Allied Military Commission in Vienna, and was eventually demobilised as an honorary lieutenant colonel.
Slightly unusually, whilst Sir Francis was sitting as a Court of Appeal judge, both his sons were practising at the bar as Queen's Counsel.
Finally Purchas was appointed a Judge of the Family Division of the High Court in 1974, at the age of 54.
In 1977, he became Presiding Judge on the South Eastern Circuit, and that year sat at Lewes Crown Court in the trial of a daughter found guilty of aiding and abetting the attempted suicide of her mother.