Jeongin Moon, David Valcin, Michael Rashkovetskyi, Christoph Saulder, Jessica Nicole Aguilar, Steven Ahlen, Shadab Alam, Stephen Bailey, Charles Baltay, Robert Blum, David Brooks, Etienne Burtin, Edmond Chaussidon, Kyle Dawson, Axel de la Macorra, Arnaud de Mattia, Govinda Dhungana, Daniel Eisenstein, Brenna Flaugher, Andreu Font-Ribera, Cristhian Garcia-Quintero, Julien Guy, Malik Muhammad Sikandar Hanif, Klaus Honscheid, Mustapha Ishak, Robert Kehoe, Sumi Kim, Theodore Kisner, Anthony Kremin, Martin Landriau, Laurent Le Guillou, Michael Levi, Paul Martini, Patrick McDonald, Aaron Meisner, Ramon Miquel, John Moustakas, Adam Myers, Seshadri Nadathur, Richard Neveux, Jeffrey A. Newman, Jundan Nie, Nikhil Padmanabhan, Nathalie Palanque-Delabrouille, Will Percival, Alejandro Pérez Fernández, Claire Poppett, Francisco Prada, Ashley J. Ross, Graziano Rossi, Hee-Jong Seo, Gregory Tarlé, Mariana Vargas Magana, Andrei Variu, Benjamin Alan Weaver, Martin J. White, Sihan Yuan, Cheng Zhao, Rongpu Zhou, Zhimin Zhou, Hu Zou

We present the first detection of the baryon acoustic oscillations (BAO) signal obtained using unblinded data collected during the initial two months of operations of the Stage-IV ground-based Dark Energy Spectroscopic Instrument (DESI). From a selected sample of 261,291 Luminous Red Galaxies spanning the redshift interval 0.4 < z < 1.1 and covering 1651 square degrees with a 57.9% completeness level, we report a ~5 sigma level BAO detection and the measurement of the BAO location at a precision of 1.7%. Using a Bright Galaxy Sample of 109,523 galaxies in the redshift range 0.1 < z < 0.5, over 3677 square degrees with a 50.0% completeness, we also detect the BAO feature at ~3 sigma significance with a 2.6% precision. These first BAO measurements represent an important milestone, acting as a quality control on the optimal performance of the complex robotically-actuated, fiber-fed DESI spectrograph, as well as an early validation of the DESI spectroscopic pipeline and data management system. Based on these first promising results, we forecast that DESI is on target to achieve a high-significance BAO detection at sub-percent precision with the completed 5-year survey data, meeting the top-level science requirements on BAO measurements. This exquisite level of precision will set new standards in cosmology and confirm DESI as the most competitive BAO experiment for the remainder of this decade.