French belongs to the long-established French family of Frenchpark, County Roscommon, who are substantial landowners who also make money in the wine trade. He is the eldest son of Arthur French MP and Alicia Magenis, daughter of Richard Magenis of Dublin and sister of Richard Magenis. He marries Margaret Costello, daughter of Edmond Costello of Edmondstown, County Mayo, and has nine children, including Arthur French, 1st Baron de Freyne, John, 2nd Baron and Charles, 3rd Baron.
In 1783, French is elected a Member of Parliament (MP) for Roscommon County in the Irish House of Commons. After the Act of Union 1800 he represents Roscommon in the Parliament of the United Kingdom. He is alleged to have been offered an Earldom if he would support the union of Ireland with Great Britain but refuses the honour. Later he also refuses a Barony with no strings attached, although in time three of his sons would hold the title Baron de Freyne. The Crown is frequently irritated by his demands for offices and favours for his brothers and sons, although such behaviour is entirely typical of an Irish politician at the time.
A critic of the policy of collective fines as a deterrent to the illicit distillation of poteen, French incurs the wrath of Chief Secretary for Ireland Robert Peel who calls him “an Abominable fellow,” but his enormous popularity in Roscommon means that he cannot be ignored. He also criticizes the continuation of martial law in Ireland.
By 1817 French is complaining of ill-health. He dies on November 24, 1820. One report at the time states that he had died “from excessive fox hunting.”