Riesling (/ˈriːslɪŋ, ˈriːzlɪŋ/ REE-sling, REEZ-ling, German: [ˈʁiːslɪŋ] ^ⓘ) is a white grape variety that originated in the Rhine region. Riesling is an aromatic grape variety displaying flowery, almost perfumed, aromas as well as high acidity. It is used to make dry, semi-sweet, sweet, and sparkling white wines. Riesling wines are usually varietally pure and are seldom oaked. As of 2004^[update], Riesling was estimated to be the world's 20th most grown variety at 48,700 hectares (120,000 acres) (with an increasing trend), but in terms of importance for quality wines, it is usually included in the "top three" white wine varieties together with Chardonnay and Sauvignon blanc. Riesling is a variety that is highly "terroir-expressive", meaning that the character of Riesling wines is greatly influenced by the wine's place of origin.

In cooler regions, such as the Mosel in Germany, Riesling wines often display apple and tree fruit notes with pronounced acidity that is sometimes balanced by residual sugar. As a late-ripening variety, Riesling can develop citrus and peach notes in warmer areas such as the Palatinate, Alsace, and parts of^[which?] Austria. In Australia, Riesling is often noted for a characteristic lime note that tends to emerge in examples from the Clare Valley and Eden Valley in South Australia.

Riesling's naturally high acidity and pronounced fruit flavors give wines made from the grape exceptional aging potential, with well-made examples from favorable vintages often developing smokey, honey notes, and aged German Rieslings, in particular, taking on a "petrol" character, as a result of the development of the compound TDN.

In 2015, Riesling was the most grown variety in Germany with 23.0% and 23,596 hectares (58,310 acres), and in the French region of Alsace with 21.9% and 3,350 hectares (8,300 acres). In Germany, the variety is particularly widely planted in the Palatinate, Rheinhessen, Mosel, Rheingau, Nahe, and Baden.

There are also significant plantings of Riesling in Austria, Slovenia, Serbia, Czech Republic, Slovakia, Luxembourg, northern Italy, Australia, New Zealand, Canada, South Africa, China, Crimea, and the United States (Washington, California, Michigan, and New York).

Riesling has a long history, and there are several written references to the variety dating from the 15th century, although with varying orthography. The earliest of these references dates from March 13, 1435, when the storage inventory of Count John IV of Katzenelnbogen in Rüsselsheim (close to the Rheingau) lists "22 ß umb seczreben Rießlingen in die wingarten" ("22 shillings for Riesling vine cuttings for the vineyard"). The spelling Rießlingen is repeated in many other documents of the time. The modern spelling Riesling was first documented in 1552 when it was mentioned in Hieronymus Bock's Latin herbal.

A map of Kintzheim in Alsace from 1348 contains the text zu dem Russelinge, but it is not certain that this reference is to the grape variety. However, in 1477, Riesling was documented in Alsace under the spelling Rissling. In Wachau in Austria, there is a small stream and a small vineyard both called Ritzling, which are claimed locally to have given Riesling its name. However, there seems to be no documentary evidence to back this up, so this claim is not widely believed to be correct.

Earlier, Riesling was sometimes claimed to have originated from wild vines of the Rhine region, without much support to back up that claim. More recently, DNA fingerprinting by Ferdinand Regner indicated that one parent of Riesling is Gouais blanc, known to the Germans as Weißer Heunisch, a variety that, while rare today, was widely grown by the French and German peasantry of the Middle Ages. The other parent is a cross between a wild vine and Traminer. It is presumed that the Riesling was born somewhere in the valley of the Rhine, since both Heunisch and Traminer have a long documented history in Germany, but with parents from either side of the Adriatic the cross could have happened anywhere on the way.