Monegasque royalty, the only child of Albert I, Prince of Monaco (1848–1922), he succeeded his father as Prince of Monaco from 1922 to 1949. His mother Lady Mary Victoria Hamilton (1850–1922) was a daughter of William Hamilton, 11th Duke of Hamilton, and his wife, Princess Marie Amelie of Baden.
Within a year of his parents’ marriage Louis was born, but his mother, a strong-willed 19-year-old, disliked Monaco and was unhappy with her husband. Shortly thereafter, she left the country permanently, and the princely couple’s marriage was annulled in 1880. Louis was raised in Germany by his mother and stepfather along with his eldest half-sister, Maria-Mathilde, and did not see his father until age 11 when he was obliged to return to Monaco to be trained for his future princely duties.
Louis’ father, Prince Albert I, was a dominating personality who had made Monaco a centre of cultural activity and whose intellectual achievements were recognized around the world. Unhappy to be living with his cold and distant father, Louis went to France as soon as he was old enough to enroll in Saint-Cyr, the French national military college. Four years later, after graduating, he was attached to the French Foreign Legion before serving with a regiment of Chasseurs d’ Afrique (African Light Horse) in Algeria.
While stationed in Algeria, he met Marie Juliette Louvet (1867–1930), a cabaret singer. Their illegitimate daughter, Charlotte Louise Juliette, was born on 30 September 1898 in Constantine, Algeria.
Louis served in the French Army for four years from 1895 to 1899, reaching the rank of lieutenant. He was awarded the médaille coloniale (Colonial Medal) and the Cross of the Legion of Honour. At the conclusion of his military service he returned to Monaco, leaving behind his mistress and daughter. At the outbreak of World War I, he re-enlisted in the French Army as a volunteer, serving as a staff officer under General Franchet d’Espèrey. Louis was made a Grand Officer of the Legion of Honour and eventually became a Brigadier General.
In 1911 a law was passed recognizing his illegitimate daughter, Charlotte, as Louis’s acknowledged heir, and making her part of the princely family. This law was later held to be invalid under the 1882 statutes. Thus another law was passed in 1918 modifying the statutes to allow the adoption of an heir, with succession rights. Charlotte was formally adopted by Louis in 1919, and became Charlotte Louise Juliette Grimaldi, Princess of Monaco, and Duchess of Valentinois.
On 26 June 1922, Prince Albert I died in Paris. Louis Grimaldi ascended to the throne as Louis II, Prince of Monaco. While his reign never achieved the grandeur of his father, Louis II left an indelible imprint on the tiny principality. In 1924 the Monaco Football Club was formed and in 1929, the first Grand Prix of Monaco automobile race was held. He collected artefacts belonging to Napoleon I which are now assembled and displayed in the Napoleon Museum attached to the Royal Palace in Monte Carlo.
Throughout World War II, Prince Louis’ vacillation in attempts at neutrality caused an enormous rift with his grandson Rainier, the heir to the throne, who strongly supported the Allies against the Nazis. For a number of months in 1944, communists participated in the Liberation administration of Monaco.
Following the liberation of Monaco by the Allied forces, Prince Louis, by 1946, was spending most of his time in Paris and on 24–27 July of that year, he married in Monaco for the first time. His wife was Ghislaine Dommanget (1900–1991), a French film actress and former wife of actor André Brulé. Absent from Monaco during most of the final years of his reign, he and his wife lived at Marchais, the family estate near Paris.
Prince Louis II died on 9 May 1949 at age 78 in the Prince’s Palace, Monaco. Hereditary Princess Charlotte ceded her succession rights to her son, Rainier, in 1944, at which time he became Hereditary Prince. When Louis died five years later, he was succeeded by his grandson, Prince Rainier III.

Link to Wikipedia biography