Princess Wilhelmina Caroline of Denmark (Danish: Vilhelmina Karoline, German: Wilhelmina Karolina) (10 July 1747 in Christiansborg Palace, Copenhagen – 14 January 1820 in Kassel), was the Landgravine consort of Hesse-Kassel and later the Electress of Hesse-Kassel by marriage to William I, Elector of Hesse.

She was one of the daughters of King Frederick V of Denmark (1723–1766), and his first spouse Louise (1724–1751), daughter of King George II of Great Britain.

At Christiansborg Palace on 1 September 1764 she married her cousin Prince William of Hesse, Count of Hanau, one of the wealthiest rulers of the period.

Wilhelmina Caroline and William had grown up together, as William and his siblings had been evacuated to the Danish royal court during the Seven Years' War (1755–1763), as his and Wilhelmina Caroline's mother were sisters. He was introduced to her as a playmate during her childhood, and it was decided already during their childhood that they should marry each other when they became adults.

One month after their wedding, Wilhelmina Caroline and William left Denmark and settled in Hesse, were her father-in-law gave William the city of Hanau as their residence, and were they lived with their own court.

During the first years of their marriage, the relationship between Wilhelmina Caroline and William was described as happy. In 1770, six years after their marriage, Hesse was visited by her brother-in-law Crown Prince Gustav of Sweden and his brother Prince Frederick, and at that occasion, the marriage between Wilhelmina Caroline and William was favorably compared to the marriage of her sister Sophia Magdalena of Denmark and Gustav of Sweden, and a suggestion was made for her and William to visit Sweden, with the unofficial thought that their example might have a good effect on her sister and royal brother-in-law. The courtier Gustaf Johan Ehrensvärd, a member of the Swedish entourage, described Wilhelmina Caroline and William on this occasion in 1770: "She is the sister of our Crown Princess, but as soon as she opens her mouth, the words come out different. She is charming, energetic, worshiped by her court... when the couple are with each other, they play as children, and during their games they produce one new child each year... I believe that it is the fault of the husband, when a woman, who is not of bad character, neglects him ..." However, this good relationship was not to last: only a few years later, William had his first mistress, Charlotte Christine Buissine, and after this, the marriage deteriorated with William being constantly unfaithful and introducing a succession of official mistresses at court, with Buissine followed by Rosa Dorothea Ritter and Karoline von Schlotheim and William producing a great number of illegitimate children.

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