Samuel Whitbread, the seventh of eight children and the youngest of five sons of Henry Whitbread, a yeoman farmer, and his second wife, Elizabeth Read, was born at Cardington near Bedford on 30th August, 1720. At the age of sixteen he was sent to London to be an apprentice at a brewery owned by John Wightman.

In December 1742 Whitbread went into partnership with Thomas Shewell. Whitbread invested £2,600 in the two small breweries owned by the Shewell family. The Goat Brewhouse made porter and at Brick Lane they produced pale and amber beers.

The porter the company produced was particularly popular. This strong, black beer, was made from coarse barley and scorched malt. The attraction of porter to Samuel Whitbread was that unlike lighter beers, it could be made in very large containers. Whitbread found it difficult to keep up with demand and in 1750 he built a new brewery at Chiswell Street. His biographer, Peter Mathias, has pointed out: "The new brewery was specifically for the single product porter, the basis for the vast brewing enterprises then being developed in London by Henry Thrale and Sir Benjamin Truman. It was named the Hind's Head brewery after the Whitbread family coat of arms. From the outset Whitbread was the leading partner financially, solely responsible for management."

In 1751 a report was published suggesting that cheap gin was causing the deaths of large numbers of people. It was estimated that in London alone, every year gin was killing 9,000 children under the age of five. As a result of this information, Parliament passed legislation to control the sale of cheap gin. Over the next few years consumption of gin fell by three-quarters as customers switched to beer. Brewers like Whitbread took advantage of this situation by promoting beer as a healthy, wholesome drink. By 1758 Whitbread was selling 65,000 barrels of porter a year. When Whitbread bought out Thomas Sewell for £30,000 in 1765, the company was one of the largest brewers of porter in England.

Samuel Whitbread married Harriet Hayton, the daughter of William Hayton of Ivinghoe, Buckinghamshire, a leading London attorney. In 1758 a son, Samuel Whitbread, was born. The couple also had two daughters. Harriet died in 1764 and five years later Whitbread married Mary Cornwallis, younger daughter of Earl Cornwallis. Tragically, the following year, Mary died in childbirth. Whitbread bought the Bedwell Park estate in Hertfordshire in 1765, and he also owned London houses, first at St Albans Street, and then at Portman Square, together with a large house in Chiswell Street by the brewery.

Whitbread became MP for Bedford in 1768. The Whitbread Brewery continued to expand and in 1769 sales had reached 90,000 barrels a year. During that decade he made an average yearly profit of £18,000. In 1786 Whitbread purchased a Boulton & Watt steam engine to grind malt and to pump water up to the boilers. This enabled the brewery to increase production to 143,000 barrels a year. This established Whitbread as the largest brewer in Britain. Peter Mathias argues: "Public renown came on 27 May 1787 with a royal visit to Chiswell Street - by the king and queen, three princesses, and an assembly of aristocrats in train - with James Watt on hand to explain the mysteries of his engine."

In 1786 Joseph Delafield explained what a difference the Boulton & Watt steam engine had made to the business: "It is built in the place where the mill horses used to stand. You may remember our wheel required six horses but we ordered our engine with the power of ten and the work it does we think equal to fourteen horses, for we grind with all our four mills about 40 quarters an hour beside raising the liquor. We began this season's work with it and have now ground about 28,000 quarters with it without accident or interruption. It consumes only a bushel of coals an hour, and we pay an annual gratuity to Boulton and Watt during their patent of £60."

Whitbread was opposed to the slave-trade and in May 1788, Charles Fox precipitated the first parliamentary debate on the issue. He denounced the "disgraceful traffic" which ought not to be regulated but destroyed. He was supported by Edmund Burke who warned MPs not to let committees of the privy council do their work for them. William Dolben described shipboard horrors of slaves chained hand and foot, stowed like "herrings in a barrel" and stricken with "putrid and fatal disorders" which infected crews as well. With the support of Samuel Whitbread, William Pitt, William Wilberforce, Charles Middleton and William Smith, Dolben put forward a bill to regulate conditions on board slave ships. The bill passed 56 to 5 and received royal assent on 11th July.

Whitbread was now a very wealthy man and in 1791 purchased Lord Torrington's Southill Estate in Bedfordshire. When Samuel Whitbread died on 11th June 1796, the Gentleman's Magazine claimed that he was "worth over a million pounds".