The Limbu script (also called Kiranti, Sirijonga or Sirijanga script) is used by about 400,000 people for writing the Limbu language spoken in Nepal and northern India. The Limbu language is also written in the Devanagari script. It was first brought to the attention of the wider world by the scholars Francis Buchanan Hamilton, A. Campbell and Brian Hodgson in the mid to late 19th century. The origins of the script are unknown; it is evident from its structure that it is of Brahmic derivation, and appears to be closely related to the Lepcha script. Limbu folklore relates that in the 9th century the Limbu king Sirijanga prayed to the goddess Saravati for wisdom as to how to devise a script for his people, and in response she revealed the story of creation to him, written in the script. The original script was modified in the mid 20th century by Imansin Cemjon and B.B. Subba, who increased the number of signs and re-assigned new values to some of the original symbols.

The Limbu script is an abugida; every letter represents a CV syllable having the inherent vowel [ɔ]. There are six other vowel sounds used in the Limbu language, [i, e, ɛ, a, o, u], which are represented using a vowel diacritic above, below or to the right of the base letter. This diacritic overrides the inherent [ɔ] vowel. There is also a diacritic mark for representing [ɔ], which is not regularly used as it is somewhat redundant. Syllable-initial vowels are written using a vowel-carrier, which in its unmarked form represents syllable-initial [ɔ], modified by the appropriate vowel diacritic.

There are twenty-eight basic consonant letters, which are not arranged in any standard canonical order. Three letters, y, r and w, also have a post-consonantal subjoining form which can be used for writing consonant clusters. The vowel which follows a consonant cluster is written above the first consonant in the cluster. For example to represent [kwa] the base letter k is written with the a diacritic above it and the subjoining form of w to the right of the k+a stack. There is no [kwa]/[kaw] ambiguity in this cluster; [kaw] would be written using the syllable-final form of w.

Syllable-final consonants can be written in one of two ways; eight letters, k, ng, t, n, p, m, r and l have a special "small" form for use at the end of a syllable. These letters do not contain an inherent vowel. Other syllable-final consonants are found mostly in loan words and are written with the letter's full form and the sa-i diacritic, which among its other functions cancels the inherent vowel in a consonant.

Vowel length is distinctive in spoken Limbu. A long vowel in open syllables is represented in writing by means of the kemphreng symbol over the initial letter. Kemphreng can also be written above the initial letters of closed syllables having a long vowel, if the closing consonant is written in its "small" form. Alternatively, the closing consonant can be marked by the sa-i sign, which in this context indicates both that the [ɔ] vowel inherent in that letter has been muted and that the preceding vowel is long.

As well as kemphreng and sa-i, a diacritic called mukphren is used, for representing glottalization; in practice this normally means a glottal stop is pronounced at the same time as a final consonant.

There is a script-specific set of numerals 0-9, but Devanagari and Latin numerals are also used; often together in the same text.

The double danda, a double vertical line, is used at the end of sentences. A Limbu question mark and exclamation mark are also used, especially by Sikkimese writers.