# The Lombok Strait
> A deep-water Indonesian passage between Bali and Lombok that carries post-Malaccamax supertankers and serves as Southeast Asia's primary submarine transit corridor.

**Meta:** type: reference · date: 2026-07-03 · heads:  · 5 takes · 2 lenses · 3 regions

## What it is

The Lombok Strait is a 60-kilometer sea lane between the Indonesian islands of Bali to the west and Lombok to the east, connecting the Java Sea and Flores Sea to the Indian Ocean. The channel ranges from 20 to 40 kilometers wide, narrowing to around 18 kilometers at its southern approach near Nusa Penida Island. Its navigable depth of at least 250 meters far exceeds the roughly 25-meter draft ceiling of the Strait of Malacca, making it one of the few passages in Southeast Asia able to accommodate post-Malaccamax vessels: very large crude carriers (VLCCs), supertankers, and bulk carriers exceeding 100,000 dead-weight tonnes (DWT). Under the United Nations Convention on the Law of the Sea (UNCLOS), the waterway forms the southern leg of Indonesia's Archipelagic Sea Lane II (IASL-II), the north-south corridor running from the Sulawesi Sea through the Makassar Strait and Flores Sea to the Indian Ocean. The Indonesian government and the International Maritime Organization (IMO) jointly administer a Traffic Separation Scheme that came into force on July 1, 2020.

## History

Indonesia ratified UNCLOS in 1985 and, as an archipelagic state under Part IV of the Convention, formally designated three Archipelagic Sea Lanes in 1996: ASL I via the Sunda Strait, ASL II via Lombok and Makassar, and ASL III via Ombai-Wetar. IMO recognized the designation the same year. A dedicated Traffic Separation Scheme for the Lombok Strait came later: the IMO Maritime Safety Committee approved it at its 101st session on June 10, 2019 (Circular COLREG.2/Circ.74), with entry into force on July 1, 2020. In October 2024, IMO's Marine Environment Protection Committee adopted Resolution MEPC.396(82), introducing additional environmental protections for the strait. The Indonesian government has periodically proposed routing more commercial traffic through Lombok to relieve congestion on the [Strait of Malacca](/ja/n/strait-of-malacca-dossier), which is projected to face saturation within the 2030s as vessel sizes continue growing.

## Current state

Around 12,861 vessels transit the Lombok Strait annually, roughly 35 per day on average. During the northern monsoon from November through March, the split between Lombok and the rival Sunda Strait shifts from roughly 55/45 to 70/30 in Lombok's favor, driving daily transits to 40-45 vessels. The strait's depth makes it the principal Southeast Asian corridor for post-Malaccamax cargo, including VLCCs carrying Middle Eastern crude oil to refineries in China, Japan, and South Korea. As of early 2026, the AUKUS trilateral security arrangement, which plans to station Australian and US nuclear-powered submarines at HMAS Stirling near Perth, Western Australia, has sharpened attention on IASL-II: the archipelagic sea-lane designation guarantees uninterrupted submerged passage, giving China's People's Liberation Army Navy (PLAN) and allied navies alike legally protected deep-water access between the Pacific and Indian oceans.

## Relationships

Indonesia holds sovereign jurisdiction over the strait and derives considerable geopolitical leverage from it: the Indonesian government has estimated that 40 percent of global maritime trade passed through its archipelagic waters in 2019. China is the dominant commercial user, routing crude oil, LNG, and manufactured goods through the strait between Middle Eastern and African suppliers and East Asian industrial markets. Australia views it as a critical national security corridor: iron ore and LNG move northward from Western Australian ports, while naval assets transit southward toward the Indian Ocean. The [Strait of Malacca](/ja/n/strait-of-malacca-dossier) is the strait's primary traffic competitor among vessels small enough to fit. The [global chokepoint network](/ja/n/shipping-chokepoints-chokepoints-backgrounder) frames how a Malacca closure would translate rapidly into a Lombok surge.

## What to watch

The AUKUS submarine basing timeline and China's naval expansion both raise questions about how competing powers will interpret IASL-II transit rights under pressure. Indonesia's parallel effort to develop Lombok island as a commercial port hub, converting free passage into economic rent through infrastructure investment, will test whether the geography can be monetized. The environmental constraints in MEPC.396(82) may impose speed or routing restrictions as traffic volumes grow. Any disruption to the [Strait of Malacca](/ja/n/strait-of-malacca-dossier), from geopolitical pressure or piracy, would reroute significant tonnage through Lombok within days, reproducing the network concentration shock documented during the [Hormuz disruption](/ja/n/strait-of-hormuz-dossier) in 2026.

## Regional takes (batched by bias / lens)

### official record
- **U.S. Energy Information Administration, World Oil Transit Chokepoints** (United States, en) — Standing EIA reference on all major chokepoints including Lombok; documents the strait as the principal deep-water alternative to Malacca for post-Malaccamax vessels carrying crude oil and LNG to East Asian markets.
  Source: https://www.eia.gov/international/content/analysis/special_topics/World_Oil_Transit_Chokepoints/
- **IMO Resolution MEPC.396(82)** (International, en) — IMO Marine Environment Protection Committee resolution adopted 4 October 2024, establishing additional environmental protection measures for the Lombok Strait within the existing Traffic Separation Scheme framework.
  Source: https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.396(82).pdf

### strategic analysis
- **Defence Connect, The Indo-Pacific's maritime choke points: Sunda and Lombok** (Australia, en) — Australian defence analysis documenting the strait's 60-km length, 20-40 km width, 250-metre minimum depth, and its role as the principal passage for post-Malaccamax vessels and submarine transit in the Indo-Pacific.
  Source: https://www.defenceconnect.com.au/maritime-antisub/4240-the-indo-pacific-s-maritime-choke-points-sunda-and-lombok
- **Daniel K. Inouye Asia-Pacific Center for Security Studies, SLOC Security in the Asia Pacific** (United States, en) — US DoD-affiliated research covering the Lombok Strait's minimum navigable width of 11.5 nautical miles and its capacity for vessels exceeding 100,000 DWT, framing its role in Asia-Pacific sea-lane security.
  Source: https://dkiapcss.edu/college/publications/occasional-paper-series-reports/sloc-security-in-the-asia-pacific/
- **Australian Institute of International Affairs, A Blessing and Curse: Indonesia's Chokepoint Power** (Australia, en) — AIIA analysis of Indonesia's leverage from controlling the Lombok, Malacca, and Sunda Straits, citing the Indonesian government's estimate that 40 percent of global maritime trade transited its archipelagic waters in 2019.
  Source: https://www.internationalaffairs.org.au/australianoutlook/a-blessing-and-curse-indonesias-chokepoint-power/

## Across the graph
- Related: [[strait-of-malacca-dossier]], [[shipping-chokepoints-chokepoints-backgrounder]], [[strait-of-hormuz-dossier]]
- Entities: Place:lombok Strait, Indonesia, China, Australia, Aukus

---
Canonical: https://rbtfl.xyz/ja/n/lombok-strait-dossier