Elsa Einstein (January 18, 1876 – December 20, 1936) was the second wife of Albert Einstein. Elsa had the surname of Einstein at birth, lost it when she took the name of her first husband Max Löwenthal, and regained it in 1919 when she married her cousin Albert.
Early stages of her life
Elsa, the daughter of Rudolf Einstein, was born in Hechingen in January 1876. She had two sisters; Paula (c. 1878–c. 1955) and Hermine (1872–1942). Rudolf was a textile manufacturer in Hechingen. During the regular visits with the family in Munich, she often played with her cousin Albert. In her Swabian dialect, she called him "Albertle". The two parted ways in 1894, when Albert left Germany to follow his family to Milan.
In 1896, Elsa married textile trader Max Löwenthal (1864–1914), from Berlin, with whom she had three children: daughters Ilse and Margot and a son who was born and died in 1903. They lived together in Hechingen. In 1902, Max Löwenthal took a job in Berlin. His family stayed in Hechingen. She divorced Max on May 11, 1908, and moved with her two daughters to an apartment above her parents on Haberlandstrasse 5, in Berlin.
She began a relationship with her cousin Albert Einstein at Easter 1912, while Albert was still married to his first wife, the physicist Mileva Marić. Einstein's divorce from Maric was final on February 14, 1919, and Elsa married him three and a half months later, on June 2, 1919. Einstein often had affairs; between the mid-1920s and his emigration to the United States in 1933, he had affairs with women named Margarete, Estella, and Ethel, and two women both named Toni. 
Elsa's and Albert's mothers were sisters, which made Elsa and Albert first cousins, and their fathers were first cousins. Ilse and Margot, Albert Einstein's first cousins once removed, had already changed their surname to Einstein and were now also his stepdaughters.
With daughters Ilse and Margot, the Einsteins formed a close-knit family. Although Albert and Elsa did not have any children of their own, Albert raised Ilse and Margot as his own. They lived in the Berlin area, also having a summer house in Caputh in nearby Potsdam.
Elsa spent most of her marriage with Albert acting as gatekeeper, protecting him from unwelcome visitors and charlatans. She also was the driving force behind building their summer house in 1929.
In 1933, Albert and Elsa Einstein emigrated to Princeton, New Jersey, USA. In autumn 1935, they moved to a house at 112 Mercer Street, bought that August, but shortly afterwards Elsa developed a swollen eye and was diagnosed with heart and kidney problems. Elsa died after a painful illness on December 20, 1936, in the house on Mercer Street.
|Offspring of Elsa Einstein and Max Löwenthal (1864–1914)|
|Ilse Löwenthal (1902-1903)|
|Margot Löwenthal (1904-1973)|
|Elsa Einstein's son (1903-1903)|
- ^ a b c d e Highfield 1993, p. 146
- ^ a b c d e Short life history: Elsa Einstein.
- ^ Highfield 1993, p. 146,287
- ^ Highfield 1993, p. 147
- ^ http://www.theguardian.com/science/2006/jul/11/internationalnews
- ^ a b Highfield 1993, p. 193
- ^ Highfield 1993, p. 203
- ^ Highfield 1993, p. 190,196
- ^ a b c Highfield 1993, p. 216
- Highfield, Roger; Carter, Paul (1993), The Private Lives of Albert Einstein, London: Faber and Faber, ISBN 0-571-17170-2