Also called tanjaq, tanjak, tanja', tanjong, or tanjung sail. The Mandar people call it sombal tanjaq because when the wind blows the lower part of the sail (peloang) would "mattanjaq" (lit. "kick").^[1][5] In colonial British records, it is sometimes written as "lyre tanjong", a misspelling of layar tanjong (layar means "sail" in Malay; layag in Philippine languages).^[6][1]

The tanja sail is a derivative of the older Austronesian triangular crab-claw sail. It developed from the fixed mast version of the crab-claw sail and is functionally identical, with the only difference being that the upper and bottom spars of the tanja sail do not converge into a point in the leading edge.^[7][8]

Early contact with Arab ships in the Indian Ocean during Austronesian voyages is believed to have resulted in the development of the triangular Arabic lateen sail. Mahdi (1999) believed that in turn, Arab ships may have influenced the development of the Austronesian rectangular tanja sail.^[9] However, there are also historians who disagree with this. Johnstone, Shaffer, and Hourani considered this sail as a genuine invention of Nusantaran people, which in turn influenced the Arabs to develop their lateen sail.^{[10]: 13 [3]: 102–103 [11]: 191–192} A research by Lynn White concludes that the Arab and Indian lateen sail is actually an adaptation the lateen sail from the Portuguese ships (caravel), which arrived post-1498.^[12] According to H. Warington Smyth, the Malay tanja sail is an adaptation and development of the primitive square sail, with boom at the head and the foot. The Malay tilted the sail forward, to bring the tack right to the deck, turning the sail into the most powerful of lifting sails on a wind.^[13]

Tanja sail can be distinguished by its canted/oblique design. The sail face is asymmetrical in shape and most of the area is elongated to the sides, rather than upward like those of lug sail.

The 3rd century book "Strange Things of the South" (南州異物志) by Wan Chen (萬震) describes large ships which originates from K'un-lun (Southern country, either Java or Sumatra). The ships called K'un-lun po (or K'un-lun bo). He explains the ship's sail design as follows:

The four sails do not face directly forward, but are set obliquely, and so arranged that they can all be fixed in the same direction, to receive the wind and to spill it. Those sails which are behind the most windward one receiving the pressure of the wind, throw it from one to the other, so that they all profit from its force. If it is violent, (the sailors) diminish or augment the surface of the sails according to the conditions. This oblique rig, which permits the sails to receive from one another the breath of the wind, obviates the anxiety attendant upon having high masts. Thus these ships sail without avoiding strong winds and dashing waves, by the aid of which they can make great speed.
— Wan Chen, "Strange Things of the South"^{[14][15]: 262}

The invention of this type of sail made sailing around western coast of Africa possible, because of its ability to sail against the wind.^{[11]: 191–192} As noted by Shaffer:

"The Malays were also the first to use balance-lug sail, an invention of global significance. Balance-lugs are square sails set fore and aft and tilted down at the end. They can be pivoted sideways, which makes it possible to sail into the oncoming wind at an angle to tack against the wind – to sail at an angle first one way and then the other, in a zigzag pattern, so as to go in the direction from which the wind is blowing. Because of the way the sides of the sail were tilted, from a distance it looked somewhat triangular.... It is thus quite likely that the Malay balance-lug was the inspiration for the triangular lateen sail, which was developed by sailors living on either side of the Malays, the Polynesians to their east and the Arabs to their west.

Precisely when the Polynesians and the Arabs began using the lateen sail remains unknown, but it would seem to have been in the last centuries B.C.E. It is known that the Arabs in the vicinity of the Indian Ocean were accomplished sailors by the first century C.E. and both they and the Polynesians apparently had the lateen sail by then"^[10]: 13

However, using Shaffer's book on this type of sail should be approached with caution. She is not the area's specialist, what she meant by "Malays" here is Austronesian people, more precisely, referring to the people residing in Indonesian areas. Major part of her book concentrates on Java.^[16]

Most Southeast Asian and Austronesian vessels used the tanja sail. This type of sail brought Austronesian sailors as far as Ghana in the 8th century,^[17] and there is probability these sailor reached the New World as early as 1420 A.D..^{[18][19][better source needed]} Some examples of vessels that use tanja sails include:

• Crab claw sail
• Lug sail
• Junk rig
• Lateen rig
• List of Indonesian inventions and discoveries