Moxie is a brand of carbonated beverage that is among the first mass-produced soft drinks in the United States. It was created around 1876 by Augustin Thompson as a patent medicine called "Moxie Nerve Food" and was produced in Lowell, Massachusetts. It has been described as having "a bitter aftertaste that some say is similar to root beer." It is flavored with gentian root extract, an extremely bitter substance commonly used in herbal medicine.

Moxie was designated the official soft drink of Maine on May 10, 2005. It continues to be regionally popular today, particularly in New England states. It was previously produced by the Moxie Beverage Company of Bedford, New Hampshire, until Moxie was purchased by The Coca-Cola Company in 2018.

The name has become the word "moxie" in American English, a noun meaning energy, determination, and spunk.

Moxie originated around 1876 as a patent medicine called "Moxie Nerve Food", by Augustin Thompson in Lowell, Massachusetts. Thompson claimed that it contained an extract from a rare, unnamed South American plant, which is now known to be gentian root. Moxie, he claimed, was especially effective against "paralysis, softening of the brain, nervousness, and insomnia".

Thompson claimed that he named the beverage after a Lieutenant Moxie, a purported friend of his, who he claimed had discovered the plant and used it as a panacea, and the company he created continued to promulgate legendary stories about the word's origin. In Maine, where Thompson was born and raised, the word moxie, apparently of Algonquian origin, appears in lake and river names, such as Moxie Falls, and in the local name of a plant, the moxie-plum; it is likely that Thompson borrowed the name from one of those. The Online Etymology Dictionary proposes that the term is an Abenaki word meaning 'dark water', while Frederic Cassidy argued that its origin was an Algonquian root maski-, meaning 'herbal infusion'.

After a few years, Thompson added soda water to the formula and changed the product's name to "Beverage Moxie Nerve Food". By 1884 he was selling Moxie both in bottles and in bulk as a soda fountain syrup. In 1885, he received a trademark for the term. He marketed it as "a delicious blend of bitter and sweet, a drink to satisfy everyone's taste." Thompson died in 1903.

In 1907, the Moxie Nerve Food Company of New England filed a lawsuit in Boston against the Modox Company and others, alleging that they had copied the ingredients of Moxie and were using the name "Modox", which closely resembles "Moxie", and were infringing upon patents and trademarks. The suit was dismissed by the judge, who said the court could not protect the legitimate part of the plaintiff's business in this case. In a later case in New York, the Moxie Nerve Food Company won a lawsuit against Modox, which subsequently went out of business.

President Calvin Coolidge was known to favor the drink, and Boston Red Sox slugger Ted Williams endorsed it on radio and in print. The company also marketed a beverage called "Ted's Root Beer" in the early sixties. Author E. B. White once claimed that "Moxie contains gentian root, which is the path to the good life."