Oṃ maṇi padme hūm̐ (Sanskrit: ॐ मणि पद्मे हूँ, IPA: [õːː mɐɳɪ pɐdmeː ɦũː]) is the six-syllabled Sanskrit mantra particularly associated with the four-armed Shadakshari form of Avalokiteshvara, the bodhisattva of compassion. It first appeared in the Mahayana Kāraṇḍavyūha sūtra, where it is also referred to as the sadaksara (Sanskrit: षडक्षर, six syllabled) and the paramahrdaya, or "innermost heart" of Avalokiteshvara. In this text, the mantra is seen as the condensed form of all Buddhist teachings.

The precise meaning and significance of the words remain much discussed by Buddhist scholars. The literal meaning in English has been expressed as "praise to the jewel in the lotus", or as a declarative aspiration, possibly meaning "I in the jewel-lotus". Padma is the Sanskrit for the Indian lotus (Nelumbo nucifera) and mani for "jewel", as in a type of spiritual "jewel" widely referred to in Buddhism. The first word, aum/om, is a sacred syllable in various Indian religions, and hum represents the spirit of enlightenment.

In Tibetan Buddhism, this is the most ubiquitous mantra and its recitation is a popular form of religious practice, performed by laypersons and monastics alike. It is also an ever-present feature of the landscape, commonly carved onto rocks, known as mani stones, painted into the sides of hills, or else it is written on prayer flags and prayer wheels.

In Chinese Buddhism, the mantra is mainly associated with the bodhisattva Guanyin, who is the East Asian manifestation of Avalokiteshvara. The recitation of the mantra remains widely practiced by both monastics and laypeople, and it plays a key role as part of the standard liturgy utilized in many of the most common Chinese Buddhist rituals performed in monasteries. It is common for the Chinese hanzi transliteration of the mantra to be painted on walls and entrances in Chinese Buddhist temples, as well as stitched into the fabric of particular ritual adornments used in certain rituals.

The mantra has also been adapted into Chinese Taoism.

Mantras may be interpreted by practitioners in many ways, or even as mere sequences of sound whose effects lie beyond strict semantic meaning.

The middle part of the mantra, maṇi padme, is often interpreted as being in the locative case, "wish-fulfilling jewel in the lotus", Sanskrit maṇi "wish-fulfilling/priceless gem, jewel, cintamani" and the locative of padma "lotus". The lotus is a symbol present throughout Indian religion, signifying purity (due to its ability to emerge unstained from the mud) and spiritual fruition (and thus, awakening). Maṇipadme is preceded by the oṃ syllable and followed by the hūṃ syllable, both interjections without linguistic meaning, but widely known as divine sounds.

However, according to Donald Lopez (citing Tibetan grammatical sources) it is much more likely that maṇipadme is in fact a noun of address, addressing in the vocative case a bodhisattva called maṇipadma, "jewel-lotus" – an alternative epithet of the bodhisattva Avalokitesvara.