The Koeri (spelt as Koiry or Koiri), also referred to as Kushwaha and more recently self-described as Maurya in several parts of northern India are an Indian non-elite caste, found largely in Bihar and Uttar Pradesh, whose traditional occupation was agriculture. According to Arvind Narayan Das, they were horticulturists rather than agriculturists. They are also recorded as performing the work of Mahajan (rural moneylenders) in credit market of rural parts of Bihar and Bengal in the 1880s. Koeris have attempted Sanskritisation— as part of social resurgence. During the British rule in India, Koeris were described as "agriculturalists" along with Kurmis and other cultivating castes. They are described as a dominant caste in various opinions.

Bihar's land reform drive of 1950s benefitted the groups like Koeris, and they were able to consolidate their landholdings at the cost of big landlords, whose possession witnessed a liquidation. It is argued that these reforms weren't percolated down to the most vulnerable groups in agrarian society, the Scheduled Castes, but the traditional agrarian relations based on caste did witness some changes. In the backdrop of this change many new landlords of post reform period hailed from groups like Koeris. In post-independence India, Koeris have been classified as Upper Backwards by virtue of being part of the group of four of the OBC communities in Bihar, who acquired land overtime, adopted improved agricultural technology and attained political power to become a class of rising Kulaks in the agricultural society of India. In some of the districts of Bihar, they have also participated in the Naxalite–Maoist insurgency against the feudal order. In parts of northern India, they, besides Yadavs, Jats and Kurmis, are considered as largest politically organised peasant community.

The Koeris are found in Saran district and are also distributed more heterogeneously across Munger, Banka, Khagaria, Samastipur, East Champaran, West Champaran and Bhojpur district. Outside India, the Koeris are distributed among the Bihari diaspora in Mauritius where they were taken as indentured labourers. They also have a significant population residing in Nepal.

In 1977, the government of Bihar introduced an affirmative action of quota in government jobs and universities which has benefitted the backward castes like the Koeris. They are classified as a “Backward caste” or “Other Backwards Caste” under the Indian government's system of positive discrimination.

Haruka Yanagisawa, Professor Emeritus of the University of Tokyo mentions in his work that Koeris along with Yadav and Kurmis were classified as upper-middle caste, who were known for their sturdy and hardy nature. Koeris have traditionally been classified as a “shudra“ caste and today Koeris have attempted Sanskritisation—the attempt by traditionally middle and low castes to rise up the social ladder, often by tracing their origins to mythical characters or following the lifestyle of higher varna, such as following vegetarianism, secluding women, or wearing Janeu, the sacred thread. The Sanskritising trend in castes of northern India, including that of the Koeris, was inspired by the vaishnavite tradition, as attested by their bid to seek association with avatars of Vishnu. Author William Pinch wrote:

"The nineteenth century antecedents of the Kushvaha- kshatriya movement reveal distinct cosmological associations with Shiva and his divine consort, Parvati. Kushvaha-kshatriya identity was espoused by agricultural community well known throughout the Gangetic north for an expertise in vegetable and (to an increasingly limited scale after the turn of twentieth century) poppy cultivation. Prominent among them were Kachhi and Murao agriculturalist of central Uttar Pradesh ,Kachhvahas of western Uttar Pradesh and Koiris of Bihar and eastern Uttar Pradesh."

Kushwaha Kshatriya Mahasabha, the caste association of Koeris, held its first session in 1922.

Some Kushwaha reformers like Ganga Prasad Gupta in Banaras argued the Koeris descended from Kusha and that they served Raja Jayachandra in their military capacity during the period of Muslim consolidation under Shuhabuddin Ghuri. He argued further that after defeat, the fear of persecution at the hands of Muslims caused the Kusvaha Kshatriya to flee into the forest in disarray and discard their sacred threads, so as not to appear as erstwhile defenders of Hinduism. The British ethnographer Herbert Hope Risley recorded various Koeri origin myths in the 1890s. According to one of them, Shiva and Parvati created Koeri and Kachhi to take care of vegetables and their flower gardens in Banaras. Writing eighty years later, Francis Buchanan-Hamilton records that Koeris of Bihar were followers of Dashanami Sampradaya while those of Gorakhpur and Ayodhya looked towards Ramanandi saints for spiritual guidance.