Katharina was born in Saint Petersburg, Russian Empire, to the later King Frederick I of Württemberg and his first wife, Duchess Augusta of Brunswick-Wolfenbüttel.

Her mother, who died when Katharina was five years old, was a sister of Caroline of Brunswick and a niece of King George III of the United Kingdom.

After the death of Katharina's mother, her father married Charlotte, Princess Royal, [2] eldest daughter of George III and thus a first cousin of his first wife.

King Jérôme, however, was unfaithful with multiple partners, including a three-year relationship with Diana Rabe von Pappenheim, but Catharina chose to turn a blind eye.

Katharina and Jerome were eventually released from house arrest and spent their remaining life together in Trieste and Switzerland, under the name of the Princess and Prince of Montfort.