Coordinates: 58°13′13″N 6°22′59″W / 58.220163°N 6.38301°W / 58.220163; -6.38301

Lewis (Scottish Gaelic: Leòdhas, pronounced [ʎɔː.əs̪], also Isle of Lewis) is the northern part of Lewis and Harris, the largest island of the Western Isles or Outer Hebrides (an archipelago) of Scotland. The total area of Lewis is 683 square miles (1,770 km²).

Lewis is, in general, the lower lying part of Lewis and Harris, with the other part, Harris, being more mountainous. The flatter, more fertile land means Lewis contains the largest settlement, Stornoway, and three-quarters of the population of the Western Isles. Beyond human habitation, the island's diverse habitats are home to an assortment of flora and fauna, such as the golden eagle, red deer and seals and are recognised in a number of conservation areas.

Lewis is of Presbyterian tradition with a rich history, having once been part of the Norse Kingdom of Mann and the Isles. Today, life is very different from elsewhere in Scotland with Sabbath observance, the Gaelic language and peat cutting retaining more importance than elsewhere. Lewis has a rich cultural heritage as can be seen from its myths and legends as well as the local literary and musical traditions.

Gilbert Newton Lewis FRS (October 23, 1875 – March 23, 1946) was an American physical chemist known for the discovery of the covalent bond (see his Lewis dot structures and his 1916 paper "The Atom and the Molecule"), his purification of heavy water, his reformulation of chemical thermodynamics in a mathematically rigorous manner accessible to ordinary chemists, his theory of Lewis acids and bases, and his photochemical experiments. In 1926, Lewis coined the term "photon" for the smallest unit of radiant energy. He was a brother in Alpha Chi Sigma, the professional chemistry fraternity, and for most of his long professorial career, a professor of chemistry at the University of California, Berkeley.

Lewis was born and raised in Weymouth, Massachusetts, where there exists a street named for him, G.N. Lewis Way, off of Summer Street. Additionally, the wing of the new Weymouth High School Chemistry department has been named in his honor. After earning his Ph.D. at Harvard under the direction of Theodore Richards, Lewis stayed as an instructor for a year before taking a traveling fellowship, studying under the physical chemists Wilhelm Ostwald at Leipzig and physicist Walther Nernst at Göttingen. While working in Nernst's lab, Nernst and Lewis apparently developed a lifelong enmity. A friend of Nernst's, Wilhelm Palmær, was a member of the Nobel Chemistry Committee. There is evidence that he used the Nobel nominating and reporting procedures to block a Nobel Prize for Lewis in thermodynamics by nominating Lewis for the prize three times, and then using his position as a committee member to write negative reports.