Yes, James Buchanan for one http://en.wikipedia.org/wiki/James_Buchanan

Yes! Only 1 and I can't remember the name but it's somewhere in the 19th century. So try Goggling it!

Many seemed to have more than one lover actually. Oh, and a wife.

According to: http://www.personal.kent.edu/~jkottman/query.htm James Buchanan was the only single US president (while in office).

James Buchanan was the only US President who was single throughout his term - he was a lifelong bachelor. Grover Cleveland was a bachelor when he was first elected, but married two years into his first term.

I don't remember any... no?

Yes, there have been nine presidents who have been single at some point during their presidency. Five presidents were single for the entire duration of their presidency. Three presidents were widowed while in office. Two presidents came to the office as bachelors (congratulations everyone, James Buchanan is one of those two). Three presidents married while in office, but only one married in the White House. When the President did not have a wife, another woman, usually a family member would step in to fill the role as White House hostess and First Lady. Also, if the President's wife was ill, or just liked her privacy, someone else would help fill the role of hostess and might perform many of the duties of First Lady, but the President's wife would still hold the title. In some cases, the Second Lady would take some of the hosting duties that were traditionally the First Lady's responsibility. The following is a list of the presidents, their wives, their First Ladies, etc. Thomas Jefferson, widower His wife Martha Wayles Skelton Jefferson passed away years before and he never remarried. His daughter, Martha Washington Jefferson Randolph, was considered First Lady of the United States, as Jefferson had no wife to fill the role. Dolley Payne Todd Madison occasionally acted as First Lady during the administration of Thomas Jefferson, fulfilling some of the ceremonial functions, but his daughter Martha is considered to be the First Lady at the time. Andres Jackson, widower His wife, Rachel Donelson Robards Jackson died shortly before he took office. His niece, Emily Tennessee Donelson, served as White House hostess and unofficial First Lady of the United States from March 4, 1829 until her death in 1836. His daughter-in-law, Sarah Yorke Jackson, served as White House hostess and unofficial First Lady of the United States from November 26, 1834 to March 4, 1837. It's the only time two women have ever simultaneously acted as unofficial First Lady. Andrew Jackson never remarried. Martin Van Buren, widower His wife, Hannah Hoes Van Buren, passed away years before and he never remarried. Angelica Singleton Van Buren, his daughter-in-law assumed the post of First Lady. John Tyler, widower while in office, remarried while in office His first wife, Letitia Christian Tyler was First Lady from April 4, 1841 until her death, September 10, 1842. Priscilla Cooper Tyler, the Tyler's daughter was already living at the White House and assisting with her mother with her duties as White House hostess to her delicate health. When Ms. Tyle died, The President asked Priscilla to assume the duties of White House hostess and First Lady. She was the first woman acting as First Lady to travel with the President as an official member of the Presidential party. A few months after his wife's death, the President started seeing Julia Gardiner. They were engaged within the year and married in secret, in New York on June 26, 1844. The now Julia Tyler, aged 26, became President Tyler's third First Lady. James Buchanan, bachelor, never married Never married. Harriet Rebecca Lane Johnston, his niece and adopted daughter (she'd requested that her favourite uncle be appointed her legal guardian when her father died when she was 11) acted as First Lady during his time in office. Chester Arthur, widower Chester Arthur's wife, Ellen Lewis Herndon Arthur, died a few months before her husband took the office of the Vice President. Half a year later when James Garfield died (assassination combined with not very capable doctors), Chester Arthur assumed the office of the President. He asked Mary Arthur McElroy to care for his young daughter Ellen and act as "Mistress of the White House." Because she had her own family in Albany, McElroy lived in Washington, D.C. only during the busy winter social season. Arthur never officially granted her the protocol of a formal position, but she was a popular and competent hostess and the procedures she and her brother developed for the social functions were used by future First Ladies for decades. Grover Cleveland, bachelor entering office (as the 22nd President), married while in office (as the 22nd President), stayed married Grover Clevland became the 22nd President of the United States on March 4, 1885. Frances Clara Folsom was born in Buffalo, New York, the daughter of Oscar Folsom and Emma Harmon-Floson in 1864. A longtime close friend of Oscar Floson, Grover Cleveland, at age 27, met his future wife shortly after she was born. He took an avuncular interest in her as a child, dotting on her, buying her baby carriages and other things as she grew up. When her father died without having written a will, the court appointed Cleveland administrator of his estate. Frances was 11 at the time. Sometime while she was in college, his feelings took a romantic turn and he proposed by letter in August of 1885, shortly after he graduation. The engagement was announced just five days before the wedding. Which is how Frances Folsom, age 21, married President Cleveland, age 49, on June 2, 1886, at the White House and became the youngest First Lady by far. Cleveland is so far the only President to be married in the White House. John Tyler married while president but in New York, and Woodrow Wilson would later marry while president, but at the home of the bride in Washington D.C. Grover Cleveland was not single for his second term in office (as the 24th President), as he was still married. Benjamin Harrison, widower while in office Harrison's wife, Caroline Lavinia Scott Harrison, was First Lady from March 4, 1889 until her death on October 25, 1892. In late 1891, she began to battle tuberculosis and her daughter, Mary Harrison McKee took up her hosting duties when she was too ill. When she passed, McKee became the First Lady. Harrison later did remarry. In 1986 he married Mary Scott Lord Dimmick, the niece of his deceased wife, and 25 years his junior. This marriage caused him to be estranged from both his children from former marriage. His second marriage produced one child. Woodrow Wilson, widower while in office, remarried while in office Wilson's first wife, Ellen Axson Wilson was First Lady from March 4, 1913 until her death on August 6, 1914. Helen Bones, Wilson's cousin and official White House hostess since the death of Ellen Wilson, introduced the President to Edith Bolling Galt in March 1915. On December 18, 1915, the two wed and Edith Bolling Galt Wilson became First Lady and held the title until Wilson left office on March 4, 1921.