Charles I of England
Charles I (19 November 1600 – 30 January 1649) was King of England, King of Scotland, and King of Ireland from 27 March 1625 until his execution in 1649. He was born into the House of Stuart as the second son of King James VI of Scotland, but after his father inherited the English throne in 1603 (as James I), he moved to England, where he spent much of the rest of his life. He became heir apparent to the three kingdoms of England, Scotland and Ireland in 1612 on the death of his elder brother Henry Frederick, Prince of Wales. An unsuccessful and unpopular attempt to marry him to the Spanish Habsburg princess Maria Anna culminated in an eight-month visit to Spain in 1623 that demonstrated the futility of the marriage negotiations. Two years later he married the Bourbon princess Henrietta Maria of France.
Charles I of England
After his succession in 1625, Charles quarrelled with the Parliament of England, which sought to curb his royal prerogative. Charles believed in the divine right of kings, and was determined to govern according to his own conscience. Many of his subjects opposed his policies, in particular the levying of taxes without parliamentary consent, and perceived his actions as those of a tyrannical absolute monarch. His religious policies, coupled with his marriage to a Roman Catholic, generated antipathy and mistrust from Reformed religious groups such as the English Puritans and Scottish Covenanters, who thought his views were too Catholic. He supported high church Anglican ecclesiastics such as Richard Montagu and William Laud, and failed to aid continental Protestant forces successfully during the Thirty Years' War. His attempts to force the Church of Scotland to adopt high Anglican practices led to the Bishops' Wars, strengthened the position of the English and Scottish parliaments, and helped precipitate his own downfall.
Anthony van Dyck
The seventh child of Frans van Dyck, a wealthy Antwerp silk merchant, Anthony painted from an early age. He was successful as an independent painter in his late teens, and became a master in the Antwerp guild in 1618. By this time he was working in the studio of the leading northern painter of the day, Peter Paul Rubens, who became a major influence on his work. Van Dyck worked in London for some months in 1621, then returned to Flanders for a brief time, before travelling to Italy, where he stayed until 1627, mostly in Genoa. In the late 1620s he completed his greatly admired "Iconography" series of portrait etchings, mostly of other artists. He spent five years in Flanders after his return from Italy, and from 1630 was court painter for the archduchess Isabella, Habsburg Governor of Flanders. In 1632 he returned to London to be the main court painter, at the request of Charles I of England.
Anthony van Dyck
With the exception of Holbein, van Dyck and his contemporary Diego Velázquez were the first painters of pre-eminent talent to work mainly as court portraitists, revolutionising the genre. He is best known for his portraits of the aristocracy, most notably Charles I, and his family and associates. Van Dyck became the dominant influence on English portrait-painting for the next 150 years. He also painted mythological and biblical subjects, including altarpieces, displayed outstanding facility as a draughtsman, and was an important innovator in watercolour and etching. His superb brushwork, apparently rather quickly painted, can usually be distinguished from the large areas painted by his many assistants. His portrait style changed considerably between the different countries he worked in, culminating in the relaxed elegance of his last English period. His influence extends into the modern period. The Van Dyke beard is named after him. During his lifetime, Charles I granted him a knighthood, and he was buried in St Paul's Cathedral, an indication of his standing at the time of his death.

Question: What monarch of three kingdoms on England, Scotland and Ireland, had his portraits painted by Flemish Baroque artist Anthony van Dyck?
Answer: Charles I of England