Princess of Wales, and one of the two women after which the Order of the Garter apparently may have been named.

Joan's father, Edmund of Woodstock, earl of Kent, was the half-brother of Edward II. Edmund was wrongfully beheaded due to a plot by Roger Mortimer and Queen Isabelle in 1330. Joan and her mother were imprisoned at Salisbury Castle for nine months. Joan spent her childhood under the care of William Montague (first earl of Salisbury) and Catherine/Katharine Montague , along with two of her three future husbands, Edward, Prince of Wales (the Black Prince), and William Montague .

When she was 12 years old she secretly married her first husband, Thomas Holand. However, Holand left for military service in France (or Prussia), and Joan's guardian, Catherine/Katharine Montague , married her to William Montague in 1340; Upon returning, Thomas petitioned Pope Clement VI to annul the marriage, which he did in 1349 by a direct papal bull; Joan had five children with Holand. Three months after Holand died in 1360, she secretly married Edward (the Black Prince, her second cousin), with whom she had two children. Her son Richard became king Richard II of England in 1377.

She became known as a peacemaker and was a patron of John Wycliffe , founder of the Lollards.

The story of the founding of the Order of the Garter has been retold many times, and apparently with relish. Costain provides a modern version of the story of the founding of the Order of the Garter .

Although Froissart declared her to be "the most beutiful woman in the whole realm of England, and the most attractive", the DMC notes that the surviving portraits and busts "do not corroborate the traditions of her beauty." She is said to have died over grief resulting from conflict between her sons by different marriages.

Joan, Katherine (Countess of Salisbury) , Queen Philippa, and "Alys" seem to be somewhat historically confused; and perhaps even confused by their contemporaries, such as Froissart.

(the "e: spelling is used here because the DMKC and AIMW, on which this is largely based, use it...)

Sources:
The DNB.
[DMKC].
[AIMW].
Froissart Chronicles.

http://www.montaguemillennium.com/familyresearch/h_1385_joan.htm