The Malaysia–Singapore border is an international maritime border between the Southeast Asian countries of Malaysia, which lies to the north of the border, and Singapore to the south. The boundary is formed by straight lines between maritime geographical coordinates running along or near the deepest channel of the Straits of Johor.Agreement between the Government of Malaysia and the Government of the Republic of Singapore to delimit precisely the territorial waters boundary in accordance with the Straits Settlement and Johor Territorial Waters Agreement 1927, signed on 7 August 1995.

The western portion of the border, beyond that delimited by the 1995 agreement, goes into the western section of the Straits of Singapore while the eastern portion of the border beyond the eastern terminus of the defined border continues into the eastern section of the straits. Outside the border defined by the 1995 agreement, there is still no formal agreement between the two countries to delimit their common borders and this has resulted in several overlapping claims. Singapore claims a territorial sea limit that extends up to 12 nautical miles and an exclusive economic zone (EEZ), while Malaysia claims a 12 nautical mile territorial sea limit.

Following the International Court of Justice (ICJ) decision on 23 May 2008 over Pedra Branca which recognised Singapore's sovereignty on the island, the new portion of the Malaysia–Singapore maritime eastern border around the island will also need to be determined. The island lies from the next easternmost point of Singapore, and southeast of the Malaysian coastline. There are two structural crossings along the border. They are the Johor–Singapore Causeway and the Malaysia–Singapore Second Link (officially known as the Tuas Second Link in Singapore). There are also international ferry and bumboat services between Pengerang at the southeastern tip of Johor, Malaysia and Changi at the eastern end of Singapore.

The border

Delimited boundary A large extent of the Malaysia–Singapore border is defined by the Agreement between the Government of Malaysia and the Government of the Republic of Singapore to delimit precisely the territorial waters boundary in accordance with the Straits Settlement and Johore Territorial Waters Agreement 1927 as being straight lines joining a series of 72 geographical coordinates roughly running about along the deepest channel (thalweg) between the western and eastern entrances of the Straits of Johor. This delineation was arrived at and agreed to jointly by the two governments and resulted in the agreement being signed on 7 August 1995.

The coordinates, which are stated in Annex 1 of the agreement, are listed below. The datum used is the Revised Kertau Datum, Everest Spheroid (Malaya), Malaysian Rectified Skew Orthomorphic projection.

Point Latitude Longitude Point Latitude Longitude Point Latitude Longitude East of Johor–Singapore Causeway E1 01° 27' 10.0" 103° 46' 16.0" E17 01° 25' 49.5" 103° 56' 00.3" E33 01° 26' 38.0" 104° 02' 27.0" E2 01° 27' 54.5" 103° 47' 25.7" E18 01° 25' 49.7" 103° 56' 15.7" E34 01° 26' 23.5" 104° 03' 26.9" E3 01° 28' 35.4" 103° 48' 13.2" E19 01° 25' 40.2" 103° 56' 33.1" E35 01° 26' 04.7" 104° 04' 16.3" E4 01° 28' 42.5" 103° 48' 45.6" E20 01° 25' 31.3" 103° 57' 09.1" E36 01° 25' 51.3" 104° 04' 35.3" E5 01° 28' 36.1" 103° 49' 19.8" E21 01° 25' 27.9" 103° 57' 27.2" E37 01° 25' 03.3" 104° 05' 18.5" E6 01° 28' 22.8" 103° 50' 03.0" E22 01° 25' 29.1" 103° 57' 38.4" E38 01° 24' 55.8" 104° 05' 22.6" E7 01° 27' 58.2" 103° 51' 07.2" E23 01° 25' 19.8" 103° 58' 00.5" E39 01° 24' 44.8" 104° 05' 26.7" E8 01° 27' 46.6" 103° 51' 31.2" E24 01° 25' 19.0" 103° 58' 20.7" E40 01° 24' 21.4" 104° 05' 33.6" E9 01° 27' 31.9" 103° 51' 53.9" E25 01° 25' 27.9" 103° 58' 47.7" E41 01° 23' 59.3" 104° 05' 34.9" E10 01° 27' 23.5" 103° 52' 05.4" E26 01° 25' 27.4" 103° 59' 00.9" E42 01° 23' 39.3" 104° 05' 32.9" E11 01° 26' 56.3" 103° 52' 30.1" E27 01° 25' 29.7" 103° 59' 10.2" E43 01° 23' 04.9" 104° 05' 22.4" E12 01° 26' 06.5" 103° 53' 10.1" E28 01° 25' 29.2" 103° 59' 20.5" E44 01° 22' 07.5" 104° 05' 00.9" E13 01° 25' 40.6" 103° 53' 52.3" E29 01° 25' 30.0" 103° 59' 34.5" E45 01° 21' 27.0" 104° 04' 47.0" E14 01° 25' 39.1" 103° 54' 45.9" E30 01° 25' 25.3" 103° 59' 42.9" E46 01° 20' 48.0" 104° 05' 07.0" E15 01° 25' 36.0" 103° 55' 00.6" E31 01° 25' 14.2" 104° 00' 10.3" E47 01° 17' 21.3" 104° 07' 34.0" E16 01° 25' 41.7" 103° 55' 24.0" E32 01° 26' 20.9" 104° 01' 23.9" West of Johor–Singapore Causeway W1 01° 27' 09.8" 103° 46' 15.7" W10 01° 26' 14.1" 103° 41' 00.0" W19 01° 21' 26.6" 103° 38' 15.5" W2 01° 26' 54.2" 103° 45' 38.5" W11 01° 25' 41.3" 103° 40' 26.0" W20 01° 21' 07.3" 103° 38' 08.0" W3 01° 27' 01.4" 103° 44' 48.4" W12 01° 24' 56.7" 103° 40' 10.0" W21 01° 20' 27.8" 103° 37' 48.2" W4 01° 27' 16.6" 103° 44' 23.3" W13 01° 24' 37.7" 103° 39' 50.1" W22 01° 19' 17.8" 103° 37' 04.2" W5 01° 27' 36.5" 103° 43' 42.0" W14 01° 24' 01.5" 103° 39' 25.8" W23 01° 18' 55.5" 103° 37' 01.5" W6 01° 27' 26.9" 103° 42' 50.8" W15 01° 23' 28.6" 103° 39' 12.6" W24 01° 18' 51.5" 103° 36' 58.2" W7 01° 27' 02.8" 103° 42' 13.5" W16 01° 23' 13.5" 103° 39' 10.7" W25 01° 15' 51.0" 103° 36' 10.3" W8 01° 26' 35.9" 103° 41' 55.9" W17 01° 22' 47.7" 103° 38' 57.1" W9 01° 26' 23.6" 103° 41' 38.6" W18 01° 21' 46.7" 103° 38' 27.2"

The Straits Settlement and Johore Territorial Waters Agreement of 1927 signed between the Britain and the Sultanate of Johor on 19 October 1927, defines the territorial sea border between Malaysia and Singapore as:

"... an imaginary line following the centre of the deep-water channel in Johore Strait, between the mainland of the State and Territory of Johore on the one side, and the northern shores of the islands of Singapore, Pulau Ubin, Pulau Tekong Kechil, and Pulau Tekong Besar on the other side. Where, if at all, the channel divides into two portions of equal depth running side by side, the boundary shall run midway between these two portions. At the western entrance of Johore Strait, the boundary, after passing through the centre of the deep-water channel eastward of Pulau Merambong, shall proceed seaward, in the general direction of the axis of this channel produced, until it intersects the limit drawn from the low water mark of the south coast of Pulau Merambong. At the Eastern entrance of Johore Strait, the boundary shall be held to pass through the centre of the deep-water channel between the mainland of Johore, westward of Johore Hill, and Pulau Tekong Besar, next through the centre of the deep-water channel between Johore Shoal and the mainland of Johore, southward of Johore Hill, and finally turning southward, to intersect the limit drawn from the low water mark of the mainland of Johore in a position bearing 192 degrees from Tanjong Sitapa."The agreement appears as a schedule in Singapore's Straits Settlements and Johore Territorial Waters (Agreement) Act 1928.

The boundary drawn by the 1995 agreement follows closely but, by virtue of being straight lines between points, does not exactly correspond with the deepest channel of the Straits of Johor as described in the 1927 agreement. As the 1995 agreement supersedes the 1927 agreement as far as any inconsistency goes, the thalweg method of determining the precise borderline is therefore replaced with the use of geographical coordinates. The 1995 agreement also states that the border will be final and, therefore, not be influenced by any variation of the depth or alignment of the deepest channel of the Straits of Johor. This is important considering frequent reclamation activities by both Malaysia and Singapore in the Straits of Johor which could alter the depth of the waterway.

Undetermined boundaries The border outside the points agreed to in the 1995 agreement has not been determined and is subject to some level of contention. In 1979, Malaysia published a mapSee map reproduced by the Singapore Ministry of Foreign Affairs in the country's response in the International Tribunal of the Law of the Sea case concerning the reclamation of lands by Singapore in the Straits of Johor . unilaterally defining its territorial waters and continental shelf, "picking up" from where the 1927 agreement left off as far as the Malaysia–Singapore border is concerned. In 2018, Malaysia published in its Federal Government Gazette changes to the Johor Bahru port limits that extrapolated from the 1995 territorial waters agreement. Malaysia's Marine Department further issued a Notice to Mariners detailing the changes in the port limits. The unilateral move drew a strong protest from Singapore's Maritime and Port Authority (MPA) who asked the mariners to ignore that notice. Singapore's Ministry of Transport (MOT) added in a statement that Malaysia was "encroaching into Singapore's territorial waters off Tuas".

Western segment

According to the 1979 map, on the western entrance to the Straits of Johor, the border starts at "Point 21", which lies near the western terminus of the border as defined by the 1927 agreement and the terminus of the border agreed to in the 1995 agreement (known as Point W25). The Malaysian border then extends southwards until "Point 17" where it then goes northeasterly till it meets the southern terminus of the Indonesia-Malaysia border delimited by the Indonesia-Malaysia continental shelf boundary agreement of 1969 and the Indonesia-Malaysia territorial waters agreement of 1971. The border between Malaysia and Singapore only runs between "Point 21" and "Point 15" where it should intersect the Indonesia-Singapore maritime border. The meeting point of the maritime territories of the three countries has not been determined.

Point Longitude (E) Latitude (N) Remarks Turning points along the continuation of Malaysia's maritime border to the west of Singapore as in its 1979 map 15 103° 22'.8 1° 15'.0 Same as Point 10 (southern terminus) of the continental shelf boundary and Point 8 of the territorial sea boundary 16 103° 26'.8 1° 13'.45 This turning point may form part of the Indonesia-Malaysia border 17 103° 32'.5 1° 1'.45 18 103° 34'.2 1° 11'.0 19 103° 34'.95 1° 15'.15 20 103° 37'.38 1° 16'.37 21 103° 36'.1 1° 15'.85 This point lies close but does not correspond with Point W25 of the 1995 territorial waters agreement

Eastern segment

The eastern continuation of the territorial waters border defined by the 1979 Malaysian map starts near the eastern terminus of the 1927 agreement border at "Point 22", whereby it goes westwards towards Singapore to "Point 23" before travelling southeasterly towards its southmost point at "Point 27". It then continues in a general easterly direction to meet the southern terminus of the Indonesia-Malaysia border as defined by their continental shelf boundary agreement of 1969. The Indonesia-Singapore border should intersect this boundary at some point but the meeting point of the maritime territories of the three countries has not been determined.

Point Longitude (E) Latitude (N) Remarks Turning point coordinates along the continuation of Malaysia's maritime border to the east of Singapore as in its 1979 map 22 104° 7'.5 1° 17'.63 This point lies close but does not correspond with Point E47 of the 1995 territorial waters agreement 23 104° 2'.5 1° 17'.42 This turning point may form part of the Indonesia-Malaysia border 24 104° 4'.6 1° 17'.3 25 104° 7'.1 1° 16'.2 26 104° 7'.42 1° 15'.65 27 104° 12'.67 1° 13'.65 28 104° 16'.15 1° 16'.2 29 104° 19'.8 1° 16'.5 30 104° 29'.45 1° 15'.55 31 104° 29'.33 1° 16'.95 32 104° 29'.5 1° 23'.9 This point is the same as Point 11 (southern terminus) of the 1969 Indonesia-Malaysia continental shelf boundary