Аннотация:MASTER OT J153539.77-461415.4 discovery - dwarf nova outburst with amplitude >5.6mFirst optical transient, detected in MASTER-OAGH (INAOE, Mexico).MASTER-OAGH of Lomonosov MSU MASTER Global Robotic Netwas mounted in December 2021 in Mexico, Guillermo Haro Astrophysics Observatory of the National Institute of Astrophysics, Optics and Electronics.MASTER-OAGH consists of twin 40cm telescope, equipped with BVRI,PP filters, 4-8 square degrees field of view and has own real-time reduction and auto-detection system (Lipunov et al., MASTER Global Robotic Net, Advances in Astronomy, 2010, 30L).We use the same scientific equipment at every MASTER observatory, it means the same photometry system and possibility to use own archive images since 2006y. for analysis.During Fermi trigger 664738369 (Ttrigger=2022-01-24 17:32:44.36UT, R.A.,Dec.(2000)=15h 36m 43s, -46d 38' 23", Rstat=5.08deg.) inspectionMASTER-OAGH auto-detection system discovered OT source at (RA, Dec) = 15h 35m 39.77s -46d 14m 15.4s at 2022-01-25.50915 UT (the second image was at 2022-01-25.54848UT with the same m_OT).The OT unfiltered magnitude is 14.4m (mlim=17.6).Taking into account the trigger time this OT should not be connected with GRB optical counterpart.The OT is seen in 3 images. There is no minor planet at this place.We have reference images in MASTER archive at 2018-09-12.91464 UT with unfiltered mlim=17.8m, at 2021-02-03 23:14:29UT with unfiltered mlim=17.6, at 2016-07-09 18:19:42UT with mlim=19m .There is no OT sources in Gaia,USNO inside 4" (22m limit in history). There is VISTA source in 0.7".Spectral observations are required.The discovery and reference images are available at:http://master.sai.msu.ru/static/OT/MASTEROTJ153539.77-461415.4.jpg