
The Undang Yang Empat (Negeri Sembilan Malay: Undang Nan Ompek; Jawi: أوندڠ يڠ امڤت) are the ruling chiefs or territorial chiefs who play an important role in the election of a new Yang di-Pertuan Besar of Negeri Sembilan, Malaysia. The Negeri Sembilan State Constitution 1959 states "The Undangs of the territories of Sungai Ujong, Jelebu, Johol and Rembau shall be persons lawfully elected..." Pt.1 Ch.3 XIV, (1). The name is believed to be derived from the Malay word undang-undang meaning "law".
Malaysia's modern day constitution confirms the status of the Undang under Article 71, 160, 181 and the Eight Schedule of Federal Constitution as Malay Ruler within the Federation. Undangs are still chosen from amongst certain noble families in the state, the succession being both matrilineal and elective following the Adat Purbakala.[citation needed]

According to Ernest Woodford Birch, the Undang Yang Empat trace their history and rank back to the four Batins (Sakai Chiefs) of Johol, Sungei Ujong, Jelebu and Klang, with Rembau later taking the position left vacant by Klang.
The Minangkabau—who settled in Negeri Sembilan, in present-day Malaysia at the end of the 17th century—were ruled by a "penghulu" or headman who was chosen from the noble families of Sakai and Jakun belonging to the Biduanda clan. These penghulu, notably those of Sungai Ujong, Jelebu, Johol and Rembau became powerful enough to exalt themselves above the other penghulu. These penghulu were later acknowledged by the sultan of the old Johor Empire as sovereign in their own territories. By the early part of the 18th century, the leaders of these four territories started using the title "Undang" to distinguish themselves from the other penghulu luak.
According to the Negeri Sembilan Constitution 1959, Pt.1, Ch.5, XIV, (1) states that the Undangs “shall be persons lawfully elected in accordance with the custom of their respective luaks.” Further, the Constitution allows for their termination as “On any of the Undangs vacating or on being removed from office in accordance with the custom of his luak…”Pt.1, Ch.5 XIV, (3).
The Undangs carry out duties such as deputy-heads of state, deputy-heads of Islam as state religion, upholding and safeguarding the special position of Bumiputera in Negeri Sembilan, attending the state opening of the legislative assembly and the election of the Yang di-Pertuan Besar of Negeri Sembilan, who is the head of state of Negeri Sembilan. The Undangs themselves cannot stand for election. According to the Negeri Sembilan Constitution 1959, the candidate "shall be a male of the Malay race, of sound mind and professing the religion of the State, who is a lawfully-begotten descendant in the male line of Raja Radin ibni Raja Lenggang" Pt.1, Ch.3 VII, (3).
The Negeri Sembilan Constitution 1959 defines the role of the Undang as a permanent members of the Dewan Keadilan dan Undangan (KDU) council, whose role is (1) "to advice on questions relating to Malay Custom..." (2) to advice "on on other matters which may be referred to it..." and (3) "to exercise such functions as may be conferred upon it by this Constitution or any other written law." Pt.1 Ch.6, XVI, (1). Here, "Malay Custom" includes "the election or succession to or removal from or vacation of office of any of the Ruling Chiefs referred to in Article XIV".
The ruling chiefs are selected among the nobility in each luak (district), following matrilineal inheritance, part of the state's adat perpatih customs.
The senior wife of an Undang has the honorific title of Tok Puan.
| Luak (District) | Title | Undang (Ruler) | Reign | Ref. |
|---|---|---|---|---|
| Sungei Ujong | Dato' Klana Petra | Dato' Haji Mubarak bin Dohak (10th, claimant) | 1993–2025 (disputed) | |
| Dato' Muhammad Faris bin Johari (11th, de jure) | 2026–present (disputed) | |||
| Abdul Rahman bin Limat (11th, claimant) | 2026–present (disputed) | |||
| Jelebu | Dato' Mendika Menteri Akhirulzaman | Dato' Haji Maarof bin Mat Rashad (16th, claimant) | 2019–2026 (disputed) | |
| Dato' Azrin bin Khairi (17th, de jure) | 2026–present (disputed) | |||
| Johol | Dato' Johan Pahlawan Lela Perkasa Sitiawan | Dato' Haji Muhammed bin Abdullah | 2016–present | |
| Rembau | Dato' Sedia Raja | Dato' Haji Abd Rahim bin Yassin (21th, claimant) | 2024–2026 (disputed) | |
| Dato' Hassan bin Ab Hamid (22th, de jure) | 2026–present (disputed) | |||