Siling labuyo is a small chili pepper cultivar that developed in the Philippines after the Columbian Exchange. It belongs to the species Capsicum frutescens and is characterized by triangular fruits that grow pointing upwards. The fruits and leaves are used in traditional Philippine cuisine. The fruit is pungent, ranking at 80,000 to 100,000 heat units in the Scoville scale.

The cultivar name is Tagalog, and literally translates to "wild chili." It is also known simply as labuyo or labuyo chili. Thai bird's eye chili are commonly confused with labuyo in the Philippines, though they are cultivars of two different species, and much larger fruit. Siling labuyo is one of two common kinds of local chili found in the Philippines, the other being siling haba (a Capsicum annuum cultivar).

Siling labuyo is generally accepted as the world's smallest hot pepper, as the fruit often measures a mere 0.20 in (0.51 cm) in length by 0.10 in (0.25 cm) in width.

It is listed in the Ark of Taste international catalog of endangered heritage foods of the Philippines by the Slow Food movement.

Siling labuyo is officially known under the cultivar name Capsicum frutescens 'Siling labuyo'. It belongs to the species Capsicum frutescens. Related cultivars of siling labuyo include tabasco, malagueta, and peri-peri.

The common name "wild chili" is derived from the Tagalog words sili ("chili") and the enclitic suffix -ng, as well as the adjective labuyo ("growing wild"), which is also a term for wild chicken or junglefowl). Other local names for it include chileng bundok, siling palay, pasitis, pasite (Tagalog); katumbal, kutitot, siling kolikot (Bisaya); katumba or lara jangay (Tausug); sili ti diablo/sairo (Ilocano); lada,sambalas, rimorimo (Bicolano); paktin (Ifugao); and luya tiduk (Maranao).

Like other Capsicum frutescens cultivars, siling labuyo has a compact habit, growing between 0.8 and 1.5 m (2 ft 7 in and 4 ft 11 in) high. They have smooth ovate to lanceolate leaves that are around 64 mm (2.5 in) in length with pointed tips. They produce small greenish-white flowers with purple stamens. These develop into a large number of small, tapering fruits that are around 25 mm (1 in) in length. The fruits are very pungent and are characteristically borne erect (pointing upwards). Immature fruits are deep green in color and usually ripen to a vivid red. Depending on maturity and the variety, they can display a range of other colors, including yellow, orange, white, or a vivid purple. Flowers and fruits are often clustered in groups of 2 to 3 at a node.

Siling labuyo fruits are small but are very hot. They measures around 80,000-100,000 Scoville units, similar to the lower end of the range for the hotter habanero chili.