Quercus subgenus Quercus is one of the two subgenera into which the genus Quercus was divided in a 2017 classification (the other being subgenus Cerris). It contains about 190 species divided among five sections. It may be called the New World clade or the high-latitude clade; most species are native to the Americas, the others being found in Eurasia and northernmost North Africa.

Members of subgenus Quercus are distinguished from members of subgenus Cerris by few morphological features, their separation being largely determined by molecular phylogenetic evidence. All are trees or shrubs bearing acorn-like fruit in which a cup covers at least the base of the nut. The outer structure of the mature pollen is one feature that distinguishes the two subgenera: in subgenus Quercus, the small folds or wrinkles (rugulae) are obscured by sporopollenin, whereas in subgenus Cerris, the rugulae are visible or at most weakly obscured.

The two subgenera are also distinguished to some extent by their different distributions. Subgenus Quercus occurs mainly in the Americas, with some species native to Eurasia and North Africa, and may be called the New World clade or the high-latitude clade. Subgenus Cerris is primarily Eurasian, with a few species in North Africa, and may be called the Old World clade or the mid-latitude clade.

The following cladogram summarizes the relationships that Denk et al. used to draw up their 2017 classification:

Quercus sect. Lobatae was established by John Claudius Loudon in 1830. The section, or part of it, has also been treated under names including Quercus sect. Rubrae Loudon and Quercus sect. Erythrobalanus Spach. It has also been treated as the subgenus Erythrobalanus and as the full genus Erythrobalanus (Spach) O.Schwarz. Its members may be called red oaks.

The perianth of the pistillate flowers has a characteristic flange-like shape. The staminate flowers have up to six stamens. The stalk connecting the perianth to the ovary is cone-shaped and often has rings. The acorns mature in two years, rarely in one year. The 'cup' (cupule) of the acorn is fused with its stalk (peduncule) forming a connective piece. Both the connective piece and the cup are covered with small triangular scales, mostly thin and membranous with broadly angled tips. The leaves typically have teeth with bristle-like extensions, or just bristles in leaves without teeth.

The section contains about 125 species native to Northern America (including Mexico), Central America, and Colombia in South America. The red oaks of Mexico are one of the groups of oaks that have most rapidly diversified into different species. Molecular evidence suggests that there are significant numbers of undescribed Quercus species in Mexico, so the number of known species in the section is likely to be an underestimate of the total diversity.

Quercus sect. Protobalanus was first established as a subgenus by William Trelease in 1922 and then later treated as a section by Otto Karl Anton Schwarz in 1936 and Aimée Antoinette Camus in 1938.