Frederick Christ Trump Sr. (October 11, 1905 – June 25, 1999) was an American real-estate developer and businessman. He was the father of Donald Trump, the 45th and 47th president of the United States, along with four other children.

Born in the Bronx in New York City to German immigrant parents, Trump began working in home construction and sales in the 1920s before heading the real-estate business started by his parents (later known as the Trump Organization). His company rose to success, building and managing single-family houses in Queens, apartments for war workers on the East Coast during World War II, and more than 27,000 apartments in New York overall. Trump was investigated for profiteering by a U.S. Senate committee in 1954 and again by New York State in 1966. Donald Trump became the president of his father's real-estate business in 1971. Two years later, they were sued by the U.S. Justice Department's Civil Rights Division for racial discrimination against black people.

According to The New York Times, Fred and his wife, Mary, provided over $1 billion (in 2018 dollar value) to their children, avoiding over $500 million in gift taxes. In 1992, Fred and Donald set up a subsidiary which was used to funnel Fred's fortune to his progeny. Shortly before his death, Fred transferred the ownership of most of his buildings to his surviving children, who several years later sold them for over 16 times their previously declared worth.

In 1927, Trump was arrested at a Ku Klux Klan demonstration, but there is no conclusive evidence that he supported the organization. From World War II onward, to avoid associations with Nazism, Trump denied his German ancestry and also supported Jewish causes.

Trump's father, the German-born Frederick Trump (originally Friedrich), amassed considerable wealth during the Klondike Gold Rush by running a restaurant and brothel for miners. Friedrich returned to Kallstadt in 1901, and, by the next year, met and married Elizabeth Christ. They moved to New York City, where their first child, Elizabeth, was born in 1904. Later that year, the family returned to Kallstadt. Fred was conceived in Bavaria, where his parents wished to re-establish residency, but Friedrich was banished for dodging the draft. The family returned to New York on July 1, 1905, and moved to the Bronx, where Frederick Christ Trump was born on October 11. Fred's younger brother, John G. Trump, was born in 1907. All three children were raised speaking German at home. In September 1908, the family moved to Woodhaven, Queens.

Many details of Trump's childhood come from autobiographical accounts and emphasize independence, learning and especially hard work – to the point of being somewhat fictionalized. At the age of 10, Trump worked as a delivery boy for a butcher. About two years later, on Memorial Day, his father died in the 1918 flu pandemic, quite suddenly according to Fred. From 1918 to 1923, Fred attended Richmond Hill High School in Queens, while working as a caddy, curb whitewasher, delivery boy, and newspaper hawker. Meanwhile, his mother continued the real-estate business Friedrich had begun. Interested in becoming a builder, Fred put up a garage for a neighbor and took night classes in carpentry and reading blueprints; he reputedly studied plumbing, masonry, and electrical wiring via correspondence courses, although other biographical sources limit his construction education to the period after high school when he was also working in the field.

After graduating in January 1923, Trump obtained full-time work pulling lumber to construction sites. He studied carpentry and became a carpenter's assistant. Trump's mother held the business in her name until he reached 21, the age of majority. The company name "E. Trump & Son" appeared in advertising by 1924, by which year Trump ostensibly used an $800 loan from his mother to complete and sell his first house. Public records, however, do not support him building until 1927, the year the company was incorporated (and following Trump's 21st birthday). Trump purportedly built 19 more homes by 1926 in Hollis, Queens, selling some before they were finished to finance others. Investigative journalist Wayne Barrett posits that Trump exaggerated the length of his career while arguing in federal court in 1934 that he should deserve a dissolved company's mortgage servicer. In 1927, Trump was arrested at a Ku Klux Klan demonstration, although there is no conclusive evidence that he supported the organization.

In 1933, Trump built one of New York City's first modern supermarkets, called Trump Market, in Woodhaven, Queens. It was modeled on Long Island's King Kullen, a self-service supermarket chain. Trump's store advertised "Serve Yourself and Save!" and quickly became popular. After six months, Trump sold it to King Kullen.