William Henry Bloomberg (January 19, 1906 – April 28, 1963) was an American businessman and bookkeeper, best known as the father of Michael Bloomberg, the billionaire entrepreneur, philanthropist, and former Mayor of New York City. Born in Boston, Massachusetts, to Russian Jewish immigrant parents, Alexander Bloomberg (a tailor) and his wife, he grew up in a modest, working-class household during a time of economic hardship for many immigrant families in early 20th-century America. The family's Jewish heritage and experiences with immigration shaped their values of hard work and resilience, which William embodied throughout his life.

Bloomberg began his professional career as a bookkeeper for a local dairy company in the Boston area. In the 1930s, leveraging his financial acumen, he acquired and founded a small dairy and egg products delivery business, which he managed successfully until his death. This venture provided stability for his family, including his wife, Charlotte Rubens (whom he married in 1933), and their two children: daughter Marjorie (born 1934) and son Michael (born 1942). Known for his frugality, strong work ethic, and community involvement in local Jewish organizations, William's influence on his son was profound, instilling lessons in business and personal responsibility that Michael later credited in his own success.

William Henry Bloomberg died of a heart attack in 1963 at the age of 57, leaving a legacy as a self-made small business owner whose modest achievements laid the groundwork for his son's extraordinary accomplishments. There are no notable controversies or legal issues associated with his life, which was marked by quiet dedication to family and enterprise.