Phenol and its substitutes are among the hazardous organic pollutants that are frequently released by different industries. The maximum amount of total phenols that can be released into aquatic habitats is 15 ppm, as determined by environmental standards. For this reason, it is crucial to develop effective methods for removing phenolic chemicals from wastewater. This work explores the possibility of using the green macroalga Ulva intestinalis Linnaeus 1753 as a biosorbent to extract phenol from aqueous solutions. The study investigated the biosorption ability of macroalgal biomass concerning multiple parameters, such as the starting pH of the solution, the concentration of phenol, the duration of contact, and the biosorption dose. The Langmuir adsorption isotherm was determined to be the most appropriate model among the others to describe how green macroalga biosorbs phenol. Regarding phenol biosorption kinetics, a pseudo-second-order model accurately characterized the process on green macroalgal biomass. The maximum capacity for phenol uptake per gram of green macroalga was determined to be 211 mg, highlighting the significant potential of this biosorbent for phenol removal. This study emphasizes the promising role of Ulva intestinalis Linnaeus as an effective biosorbent for the elimination of phenol from aqueous solutions, contributing to the development of sustainable and efficient wastewater treatment strategies.