|Possible time of origin||over 45,000 years old|
|Possible place of origin||Southeast Asia or Southern China|
Primary descendant: NO1 (M214/Page39);
N (M231) and O (M175).
Haplogroup NO (F549/M2335/S22380/V4208) is a human Y-chromosome DNA haplogroup. NO is the only primary descendant of Haplogroup K2a1 (M2313), which in turn is a primary descendant of Haplogroup K2a (M2308). 
Before 2016, it was generally considered that "NO" and "K2a" were identical and constituted a primary branch of Haplogroup K2. However, researchers such as Poznik et al. discovered Y-DNA in ancient remains and living individuals that had some, but not all, of the mutations regarded previously as peculiar to NO, but lacked any of the SNPs identifying other primary clades of K2. Poznik et al. therefore considered that K2a and NO constituted "grandparent" and "grandchild" clades, and proposed that the name Haplogroup K2a1 be assigned to the Y-DNA of individuals who belonged to K2a, but did not belong to NO.
While there are some reports of NO* or NO1* being found in living individuals, these haplogroups are not well-researched. Further research may instead identify them as belonging to N* (M231), N1, or the provisional subclade N2 (F3373/M2283/Page56/S323). These cases include:
- 5.7% (2/35) of Bouyei males, in China or Vietnam;
- a pool of four samples of Japanese males at 2.9% (6/210), particularly in Tokushima Prefecture at a rate of 5.7% (4/70), and;
- small proportions of samples from Yizu, Malays, Sô, Mongolians, Daurs, Manchurian Evenks, Hezhes, Huis, Yaos, South Koreans, Fiji (1/107 = 0.9%), Futuna 5%, Niue 3.5%, Tuvalu 3.6%, and Samoa 3%.
Two sets of ancient remains previously considered as possibly belonging to NO have since been reclassified upstream to K2a.
- Ust'-Ishim man dates from approximately 45,000 BP and was found in Omsk Oblast, Russia.  (Until 2016 these remains were erroneously classified as K2*.)
- Oase 1: the remains found in Romania of a male who lived 37,000-42,000 years BP.
Likewise, cases previously regarded as possible examples of NO* or NO1*, and since ruled out, include:
- two Han Chinese males previously found to be negative for M175 (i.e. Haplogroup O) and LLY22g (an obsolete, possibly inaccurate marker for N1), have subsequently have been found to belong to N* (N-M231), and;
- a clade first identified in South India, defined by the SNP M147 and labelled "pre-NO" and "Haplogroup X", among other names, was found to be a sibling of NO (K2a) within Haplogroup K2 (K-M526); the new clade was renamed K2e.
- NO (F549/M2335/S22380) – also known as Haplogroup K2a
- Human Y-chromosome DNA haplogroup
- Genealogical DNA test
- Y-chromosome haplogroups in populations of the world
|Phylogenetic tree of human Y-chromosome DNA haplogroups [χ 1][χ 2]|
|A00||A0-T [χ 3]|
|A0||A1 [χ 4]|
|I||J||LT [χ 5]||K2|
|L||T [χ 6]||K2a [χ 7]||K2b [χ 8]||K2c||K2d||K2e [χ 9]|
|K2a1||K2b1 [χ 10]||P [χ 11]|
|NO||S [χ 12]||M [χ 13]||P1||P2|
- Rootsi, Siiri; Zhivotovsky, Lev A; Baldovič, Marian; Kayser, Manfred; Kutuev, Ildus A; Khusainova, Rita; Bermisheva, Marina A; Gubina, Marina; Fedorova, Sardana A; Ilumäe, Anne-Mai; Khusnutdinova, Elza K; Voevoda, Mikhail I; Osipova, Ludmila P; Stoneking, Mark; Lin, Alice A; Ferak, Vladimir; Parik, Jüri; Kivisild, Toomas; Underhill, Peter A; Villems, Richard; et al. (2007). "A counter-clockwise northern route of the Y-chromosome haplogroup N from Southeast Asia towards Europe". European Journal of Human Genetics. 15 (2): 204–211. PMID 17149388. doi:10.1038/sj.ejhg.5201748.
- G. David Poznik et al., 2016, "Punctuated bursts in human male demography inferred from 1,244 worldwide Y-chromosome sequences" Nature Genetics, no. 48, pp. 593–599.
- ISOGG 2016 Y-DNA Haplogroup Tree 2016 (2 August 2016).
- Hammer et al. (2005) "Dual origins of the Japanese: common ground for hunter-gatherer and farmer Y chromosomes," The Japan Society of Human Genetics, 2005
- Xue, Yali; Zerjal, Tatiana; Bao, Weidong; Zhu, Suling; Shu, Qunfang; Xu, Jiujin; Du, Ruofu; Fu, Songbin; Li, Pu; et al. (2006). "Male demography in East Asia: a north-south contrast in human population expanion times". Genetics. 172 (4): 2431–2439. PMC . PMID 16489223. doi:10.1534/genetics.105.054270.
- Tatiana M. Karafet, Brian Hallmark, Murray P. Cox et al., "Major East-West Division Underlies Y Chromosome Stratification Across Indonesia," MBE Advance Access published March 5, 2010.
- Karafet; Mendez, F. L.; Meilerman, M. B.; Underhill, P. A.; Zegura, S. L.; Hammer, M. F.; et al. (2008). "Abstract New Binary Polymorphisms Reshape and Increase Resolution of the Human Y-Chromosomal Haplogroup Tree". Genome Research. 18 (5): 830–8. PMC . PMID 18385274. doi:10.1101/gr.7172008.
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