Zapornia is a recently revalidated genus of birds in the rail family Rallidae; it was included in Porzana for much of the late 20th century. These smallish to tiny rails are found across most of the world, but are entirely absent from the Americas except as wind-blown stray birds (which are regularly encountered on the Atlantic coasts however). A number of species, and probably an even larger number of prehistorically extinct ones, are known only from small Pacific islands; several of these lost the ability to fly in the absence of terrestrial predators. They are somewhat less aquatic than Porzana proper, inhabiting the edges of wetlands, reedbelts, but also drier grass- and shrubland and in some cases open forest.

They are medium brown to blackish above, at least from the neck backwards but usually also on the top of the head, uniformly coloured or with some rather inconspicuous (unlike the boldly spotted Porzana proper) pattern of some blackish and/or whitish spots on the wings and back and/or a grey stripe above the eyes. The lower parts, from the bill to the legs, have grey plumage in most species - ranging from pale to almost black -, but are light ruddy-brown in a few. Between legs and tail, the plumage is brown to black, and in many species features more or less conspicuous whitish barring as in many other genera of rails (including Porzana proper). Some species (in particular small-island ones) appear uniformly drab brown or blackish-grey, with little discernible pattern when not seen up close. The eyes are usually red to chestnut-brown; the bill is short and straight by rail standards, greenish-yellow in most species, but bright yellow or blackish in a few. The legs have a greenish to reddish colouration even in the otherwise quite uniformly dusky species, and in some species are bright red

The genus Zapornia was introduced in 1816 by the English zoologist William Elford Leach in a catalogue of animals in the British Museum. He included a single species, the little crake, which is therefore the type species. The genus name is a near-anagram of the French ornithologist Louis-Pierre Vieillot's genus Porzana.

However, Leach's proposal was not widely adopted. During the 1840s Zapornia was used as a "wastebin taxon" for newly-discovered small rails from all over the world, few of which actually belong to today's Zapornia clade; in 1880, even the Slender-billed flufftail was placed here, which eventually turned out to be no rail (family Rallidae) at all, but rather an aberrant crake-like member of the flufftail family Sarothruridae. Subsequently, Leach's genus was generally synonymized with Porzana, assuming that species such as the Little and Baillon's crake were merely diminutive representatives of that genus. From the late 19th to the mid-20th century, any newly-discovered Zapornia crakes were either assigned to new and usually monotypic genera, or – increasingly often – lumped with their presumed relatives in Porzana. In his 1973 review of rail systematics, Storrs Olson noted that the mutual delimitation of the (loosely-circumscribed) Porzana and Amaurornis was "[o]ne of the most difficult problems in rail taxonomy" and found no way to resolve it to his satisfaction. He concluded that the two genera were polyphyletic with regard to each other, and recommended including the numerous small segregate genera of Pacific island crakes in Porphyria, and the African crakes sometimes separated as Limnocorax in Amaurornis, until a satisfying solution for the delimitation of the two larger genera could be proposed.

The first cladistic analyses, using morphological data, found it almost impossible to resolve any phylogenetic structure in Porzana and similar genera, but indicated that the entire group was closely related to Amaurornis bush-hen and the Laterallus crakes, as well as to coots (Fulica) and moorhen (Gallinula). Molecular phylogenetic studies starting in 2002 revealed that Porzana proper was a well-distinct lineage within the entire aforementioned group, to which the subfamily name Himanthornithinae was applied as it also included the singular Nkulengu rail of genus Himantornis, a highly aberrant tropical rainforest species that was long considered to be the most "primitive" living rail. However, molecular data places not only the Nkulengu rail within the subfamily containing Porzana and its allies, but also the huge swamphen (Porphyrio) which morphological analysis had resolved as another one of the most ancient extant lineages of rails (although Olson in 1973 had correctly allied them with the moorhen and Porphyrio). Unlike the other rail subfamily, Rallinae, which includes mostly mid-sized amphibious species, the Himanthornithinae unite both very large and very small rails, as well as decidedly aquatic and strongly terrestrial lineages; it is thus unsurprising that the morphological data could not resolve such an adaptive radiation to satisfaction.

As for the Zapornia crakes, they were found to be well distinct from Porzana, leading to the reinstatement of the old genus. In addition, some species traditionally placed in Amaurornis were found to actually belong in Zapornia, confirming Olson's 1973 suspicions. Surprisingly (except from a biogeographical perspective), the closest living relatives of Zapornia were found to be a group of South Asian crakes of genus Rallina, whose range is essentially surrounded by that of Zapornia. Rallina crakes are adapted to a more terrestrial habitat and thus differ more strongly from Zapornia in anatomy than might be expected given their close relationship; also, Rallina as traditionally circumscribed included a number of species which – similar to the Slender-billed flufftail initially being placed in Zapornia – actually belonged to the flufftail family and are nowadays separated as genus Rallicula. The morphology of Rallina is thus strongly convergent with the unrelated Rallicula flufftails, as well as strongly divergent from its actual closest relatives in Zapornia, causing studies which only utilize morphological data to fail recovering their true relationships.

The genus contains the following extant species:

Due to the uncertain relationships of the extinct species (see below), the internal phylogeny of Zapornia is not well resolved. Several clades can be distinguished with some certainty, however, and recognized as subgenera. Sometimes they are even elevated to full genus level, but given the conflicting data about the basal radiation of Zapornia, this remains conjectural for the time being. In particular the African endemics Black crake and Sakalava rail are the source of much uncertainty; they were considered closely related, even a superspecies, and allied with the Black-tailed crake when these three were still included in Amaurornis. This assumption was not based on quantitative analyses however, but on the similar appearance of Sakalava rail and Black-tailed crake and the fact that the Sakalava rail occurs on the western coast of Madagascar while the Black crake is found on the African mainland across the Mozambique Channel. Altogether however, the Sakalava rail remains little-known, and consequently has rarely been included in modern studies.