Algal in the state of Uttar Pradesh, algal exploration and taxonomical work have been carried out in all-natural types of freshwater ecosystems, from a small puddle or pond to a big lake or a little stream or a tortuous river. In 1928, Y. Bharadwaja, who had trained under FE Fritsch, returned from London and started the documentation of algae. Most of his work was survey-based that was confined to Varanas (Bharadwaja 1928, 1930, 1935), followed by C.B. Rao (1935; 1936, 1937) from freshwater bodies. R.N. Singh (1939-1954) reported the algal flora of paddy fields and studied the nitrogen fixation of cyanobacteria in soil and usar soil reclamation through Cyanophyceae. Singh (1959), documented the algal flora of Mirzapur district. Prasad (1952) reported the heterocystous cyanobacteria, while Gupta (1956) documented the algal flora of Allahabad. Pandey and Mitra (1962) recorded a new species of Anabaenopsis ambigua and Pandey (1965) documented algae in the rice fields of Ballia and Ghazipur. Chandhykok (1966) and Hortobagyi (1969) recorded algal species from the Yamuna River. Many other researchers explored various algal species from diverse regions of Uttar Pradesh, such as Nair (1967) from Kanpur district, Prasad and Mehrotra (1976, 1979, 1980) from rice fields, Khan (1985) reported from the rice field of Sultanpur, Kolte and Goyal (1986), and Suseela and Goyal (1995) from rice fields, Misra and Srivastava (2005) from Gonda and Bahaich, Tiwari (2005) from Agra. Besides, there are several PhD theses which also documented the algal flora of Uttar Pradesh. However, the cyanobacterial strains were first recorded by Bharadwaja (1928) and up to Singh et al. (2023). The chlorophycean algal group were first documented by Randhawa (1936), Saxena (1962a), followed by several workers up to Saini et al. (2023). Singh (1960), first documented Rhodophyceaen alga followed by Pandey (1965), Pandey et al. (1976), Chaturvedi et al. (1978, 1979) Yadav and Kumano (1985) and Necchi et al. (2015). The documentation of euglenophycean algae was first initiated to document by Singh (1948) from Varanasi followed by Hortobágyi (1969), Singh and Saxena (1969), Pandey and Chaurvedi (1979), Philipose (1982, 1984, 1988), Pandey (1985), Habib and Pandey (1990), Tiwari (2005) up to Verma (2021); while the species belonging to Bacillariophyceae were documented by Singh (1939), Verma (2021), Srivastava (2021); however Sarma and Shyam (1974), Shyam and Sarma (1980) reported freshwater Dinophyceae (Mitra, 1951), Chrysophyceae (Randhawa, 1939) followed by Saxena (1962b) and Awasthi (2015) documented Xanthophyceae from this region.
