Arnis, also known as kali or eskrima/escrima, is the national martial art of the Philippines. These three terms are, sometimes, interchangeable in referring to traditional martial arts of the Philippines ("Filipino Martial Arts", or FMA), which emphasize weapon-based fighting with sticks, knives, bladed weapons, and various improvised weapons, as well as "open hand" techniques without weapons.

There were campaigns for arnis along with other Philippine martial arts to be nominated in the UNESCO Intangible Cultural Heritage Lists; and as of 2018, UNESCO has inscribed nine martial-arts-related intangible heritages.

Arnis comes from arnés, the Old Spanish for "armour" (harness is an archaic English term from same root). It is said to derive from the armour costumes used in traditional Moro-moro stage plays, where actors fought mock battles with wooden swords.^{[unreliable source?]} Arnes is also an archaic Spanish term for weapon, used as early as 1712. (Arms is an English term from the same root)

Eskrima (also spelled escrima) is derived from the Spanish word for fencing, esgrima. Their cognate in French is escrime and is related to the English term 'skirmish'.

The name kali is most likely derived from the pre-Hispanic Filipino term for blades and fencing, kalis (Spanish spelling: "calis"), documented by Ferdinand Magellan's expedition chronicler Antonio Pigafetta during their journey through the Visayas and in old Spanish to Filipino Mother Tongue dictionaries and vocabulary books dating from 1612 to the late 1800s, such as in Vocabulario de Lengua Tagala by Fr. Pedro de San Buenaventura. The term calis in various forms was present in these old Spanish documents in Ilocano, Ibanag (calli-t; pronounced as kal-lî), Kapampangan, Tagalog, Bicolano (caris), Waray (caris), Hiligaynon, Cebuano (calix, baladao – "kalis balaraw/dagger" and cales), and Moro-Maguindanao in Mindanao (calis – the kris, weapon). In some of these dictionaries, the term calis refers to a sword or knife kris or keris, while in others it refers to both swords and knives and their usage as well as a form of esgrima stick fighting. The first to use this term in reference to Filipino martial arts was Buenaventura Mirafuente in 1948. While Mirafuente posits that the original term was kali and that the letter "S" was added later, the late Grandmaster Remy Presas suggests that the "S" was dropped in modern times and became presently more known as kali in FMA circles.

There exist numerous similar terms of reference for martial arts such as kalirongan, kaliradman, and pagkalikali. These may be the origin of the term kali or they may have evolved from it.

In their book Cebuano Eskrima: Beyond the Myth however, Dr. Ned Nepangue and Celestino Macachor contend that the term kali in reference to Filipino martial arts did not exist until the Buenaventura Mirafuente wrote in the preface of the first known published book on arnis, Mga Karunungan sa Larong Arnis by Placido Yambao, the term kali as the native mother fighting art of the Philippine islands.

Practitioners of the arts are called arnisador (male, plural arnisadores) and arnisadora (female, plural arnisadoras) for those who call theirs arnis, eskrimador (male, plural eskrimadores) or eskrimadora (female, plural eskrimadoras) for those who call their art eskrima, and kalista or mangangali for those who practise kali.