Robert Stephenson FRS, HonFRSE, FRSA, DCL (Hon. causa) (16 October 1803 – 12 October 1859) was an English civil engineer and designer of locomotives. The only son of George Stephenson, the "Father of Railways", he built on the achievements of his father.

Robert Stephenson became an apprentice under mining engineer Nicholas Wood after completing his education in 1819. In 1821, he and his father surveyed the Bishop Auckland area to help Edward Pease build a railway that would transport coal from the area to Darlington and Stockton-on-Tees. In 1823, the Stephensons and Pease founded Robert Stephenson and Company to manufacture locomotives; the company designed such locomotives as the Lancashire Witch in 1828 and the John Bull in 1831, the latter of which became the first steam locomotive to run in New Jersey.

Throughout the 1830s Robert oversaw the construction of several railways, including the Canterbury and Whitstable Railway, the Bolton & Leigh railway, the Warrington & Newton Railway and the Leicester and Swannington Railway. He drew the plans for the London and Birmingham Railway, which opened in 1838. In 1832 he was appointed surveyor for a project to build a railway between Lanehead Farmhouse and Consett in County Durham, but the railway line closed in 1840, six years after its completion. In 1839 he spent three months in France, Spain and Italy advising on railways, and after returning to England he advised Parliament and arbitrated in disputes between railway companies and contractors. He was made Knight of the Order of Leopold in 1841 for his improvements to locomotive engines.

In 1845 Robert designed an iron bridge that would cross the River Dee; the Dee bridge was completed in 1846 but collapsed under a locomotive, causing the deaths of five people. Robert was accused of manslaughter during the inquest, but a verdict of accidental death was ultimately returned. He also designed the Britannia Bridge, which crosses the Menai Strait and consists of four tubes; it was opened to public traffic in 1850. The High Level Bridge, another of his works, crosses the Tyne and was opened in 1849 by Queen Victoria. She offered Robert a knighthood, but he refused.

Robert, who was a member of the Conservative Party, was elected as the Member of Parliament for Whitby; he held the position until his death in 1859.

Robert has been called the greatest engineer of the 19th century. Stephenson's death was widely mourned, and his funeral afforded marks of public honour. He is buried in Westminster Abbey.

Robert Stephenson was born on 16 October 1803, at Willington Quay, east of Newcastle upon Tyne, to George Stephenson and Frances (née Henderson), usually known as Fanny. She was twelve years older than George, and when they met she was working as a servant where George was lodging. After marrying, George and Fanny lived in an upper room of a cottage; George worked as a brakesman on the stationary winding engine on the Quay, and in his spare time he cleaned and mended clocks and repaired shoes.

In 1804, George became a brakesman at the West Moor Pit, and the family moved to Killingworth. Fanny's health deteriorated, and she died on 14 May 1806. Robert was first sent to a village school 1+1⁄2 miles (2.4 km) away in Long Benton. George had received little formal education but was determined that his son would have one and so sent the eleven-year-old Robert to be taught at the Percy Street Academy in Newcastle. Robert became a member of the Newcastle Literary and Philosophical Society and borrowed books for him and his father to read. In the evenings, he would work with his father on designs for steam engines. In 1816 they made a sundial together, which is still in place above the cottage door.