Cider apples are a group of apple cultivars grown for their use in the production of cider (referred to as "hard cider" in the United States). Cider apples are distinguished from "cookers" and "eaters", or dessert apples, by their bitterness or dryness of flavour, qualities which make the fruit unpalatable but can be useful in cidermaking. Some apples are considered to occupy more than one category.

In the United Kingdom, the Long Ashton Research Station categorised cider apples in 1903 into four main types according to the proportion of tannins and malic acid in the fruit. For cider production, it is important that the fruit contains high sugar levels which encourage fermentation and raise the final alcohol levels. Cider apples therefore often have higher sugar levels than dessert and cooking apples. It is also considered important for cider apples to contribute tannins, which add depth to the finished cider's flavour.

In 1903, Professor B.T.P. Barker, the first director of the Long Ashton Research Station (LARS) in Bristol, England, established an analytical classification system for cider apples based on tannin and malic acid percentages in pressed juice. This system is divided into four categories, which are as follows:

Long Ashton's classification system also included a three-level classification of tannin: "full" for an apple with pronounced tannins (e.g. a "full bittersweet" such as Chisel Jersey, "mild" for light tannins such as Cummy Norman, and "medium" such as Dabinett.

Tannins are further sometimes categorised as "hard" or "soft", for bitter and astringent tannins respectively.

British cidermakers normally blend juice from apples of multiple categories to ensure a finished cider with a balanced flavour and for the best and most consistent quality. While traditional ciders were made from whatever apples were available locally, the blend of sugar, acid and tannin required for a successful cider is difficult to achieve from any single cultivar with the possible exception of some bittersharps. As bittersharps are rare, a common modern approach is to use a range of bittersweet varieties with some sharps, or a cooking apple such as the readily available Bramley, to balance the acidity. Sharps, with their high acid content, also keep the cider's pH below 3.8 to prevent spoilage; sweets help provide adequate sugar for fermentation to the proper alcohol content.

In addition to the Long Ashton Research Station classification, Charles Neal has written about a French classification system. In France and Spain, the system has an intermediate category called acidulée or acidulada respectively, which is sometimes used to classify cider apples that are semi-tart and have low tannin content. Similar to the English system, acidity and tannins are considered. Apples are classified as follows:

In the US, there are four regions where cider apples are grown in orchards: the Northeast, Mid-Atlantic, Midwest, and Northwest. Out of the twenty most commonly grown cider apple varieties, half originate from England, two come from France, and the rest originate in America. Most special cider cultivars for European ciders are bittersweets and bittersharps, which have high tannin content. There are not a lot of cultivars with high tannins readily available in the U.S. Most ciders in the United States are made from culled dessert apples that are generally sweets and sharps. There is no systematic classification of North American apple cultivars for cider-making purposes. However, there is a database for apple varieties called the U.S. National Plant Germplasm System (NPGS).