Results on the autoignition and stabilization of ethanol hydrothermal flames in a Supercritical Water Oxidation (SCWO) reactor operating at constant pressure are reported. The flames are observed as luminous reaction zones occurring in supercritical water; i.e., water at conditions above its critical point (approximately 22 MPa and 374 degrees C). A co-flow injector is used to inject fuel (inner flow), comprising an aqueous solution ranging from 20%-v to 50%-v ethanol, and air (annular flow) into a reactor filled with supercritical water at approximately 24.3 MPa and 425 degrees C. Results show hydrothermal flames are autoignited and form diffusion flames which exhibit laminar and/or turbulent features depending upon flow conditions. Two orthogonal camera views are used; one providing a backlit shadowgraphic image of the co-flow jet and the other providing color images of the flame. In addition, spectroscopic measurements of flame emissions in the UV and visible spectrum are discussed.