Maechi or Mae Chee (Thai: แม่ชี; IPA: [mɛ̂ː.t͡ɕʰiː]), "respected mother" (แม่ + honorific suffix "-ji"), are Theravada Buddhist Nuns in Thailand. As female monastics ordained under The Eight or Ten Precepts (i.e., more than the Five Precepts taken by laypersons), they formally occupy a position similar to sāmaṇerī and wear white robes, but are in practice resemblant of Theravāda bhikkhus - renunciants who have dedicated their life to Buddhist practice, meditation, vowing celibacy and ascetisicm.

Like the thilashin of neighbouring Myanmar and the dasa sil mata of Sri Lanka, maechi occupy a position somewhere between that of an eight-precept Upasikā and a Buddhist Monk.

Like bhikkhus, maechis shave their heads and undertake precepts not generally observed by lay followers. Maechis most commonly receive these precepts from a qualified senior monk in a formal ordination ceremony. Maechis wear white robes, distinguishing them from both monks and lay people.

They are not ordained under 311 precepts ('bhikkhuni'). The full ordination is debated or illegal for women in some countries including Thailand since the original lineage of the historical Bhikkhuni Sangha dating back to Gautama Buddha died out between the 11th and 14th Century in Sri Lanka. In 1928 a law was created by the Supreme Patriarch of Thailand in line with attempts to preserve the distribution period (Sāsana) of the traditional early Buddhist Teachings. It is partly based on the traditional interpretation of rules regarding bhikkhunī ordinations according to the Vinaya Pitaka, requiring multiple senior bhikkhunis to initiate new nuns into the order, as well as the absence of fully trained female elders to facilitate suitably qualified apprenticeship for the female monastic aspirants.

As of 1998, the Theravadin Order of Nuns (Bhikkhunī) had been without any members for at least 700 years. While the officially recognized male monastic communities has traditionally received considerable oversight and assistance from various government ministries, only in the 20th century did the Thai Sangha begin to take an organized role in providing for the needs of maechis specifically. An institute now attempts to roughly track the number of nuns in the country, and provides funds that can be used for educational opportunities. They do not have the same legal recognition as bhikkhus by the Thai government and are not eligible for all monastic benefits such as free passage on public transportation, but they are like monks, omitted from voting or standing for civil elections.

Temporary maechis, who typically do not shave their heads, are called chi phram (Thai: ชีพราหมณ์; RTGS: chi phram).

Most maechis live on or close to wat and temple grounds. They sometimes share responsibilities with resident bhikkhus in supporting the temple, and often take on roles helping the monks in certain areas where the latter are more restricted by the Vinaya. Smaller numbers of maechis live in their own communities, which may or may not be associated with a local monastery.

Historically, little is known about the status and lives of maechis prior to Western contact with the kingdoms that preceded the modern state of Thailand. European observers in the 17th century reported seeing white-robed, shaven-headed nuns who lived on the grounds of Buddhist temples.