He was prime minister for the Archbishop-Elector of Cologne, and at the same time worked for Louis XIV of France influencing affairs in the Empire.

Born on 10 April 1626 in Heiligenberg, Franz was an elder son[clarification needed] of Egon VIII of Fürstenberg-Heiligenberg (1588–1635), who served with distinction as a Bavarian general in the Thirty Years' War.

[5] He soon gained strong influence over the elector, and Franz and his brother Wilhelm were instrumental in guiding the Archbishop-Elector as a tool of the aggressive policy of Louis XIV of France.

[2] When Ferdinand III died in 1657, the Cardinal asked Franz to help him influence the selection of the next Emperor, even going so far as to suggest Louis XIV of France for the role.

[8] On 4 June 1658, Lionne, Franz, and Wilhelm signed an agreement detailing French support for the counts should they continue to work "for all the plans and interests of His Majesty in Germany".

[11] When the previous prince-bishop of Strasbourg died in 1662, the crown of France offered large amounts of cash to get Franz elected as the successor.

[2] In 1673, Franz moved into the newly renovated Château des Rohan (Mutzig), which became the residence of the bishops of Strasbourg.

[14] On the conclusion of a treaty between the emperor and the elector of Cologne, on 11 May 1674, Franz was deprived of all his preferments in Germany, and was compelled to take refuge in France.