Fire-resistant polymer matrix composites have gained considerable importance in structural, transportation, and infrastructure applications due to increasing fire safety requirements combined with the demand for high mechanical performance. In the present study, compression-moulded S2 glass fiber reinforced phenolic composites incorporating 15 wt.% ammonium polyphosphate (APP) were developed and experimentally investigated for fire-resistant panel applications. The composite laminates were fabricated using bidirectional woven S2 glass fabric and resol-type phenolic resin through compression moulding to achieve uniform consolidation, controlled thickness, and reduced void content. Mechanical characterization was carried out using tensile, flexural, and Izod impact testing according to ASTM standards. The developed composite exhibited tensile strengths in the range of 260–300 MPa with tensile modulus values close to 10 GPa, indicating effective stress transfer between fibers and matrix. Flexural testing revealed strengths between 410–430 MPa with flexural modulus around 15 GPa, demonstrating excellent bending performance without severe degradation due to APP incorporation. Impact testing confirmed moderate energy absorption capability despite the brittle nature of phenolic matrices. Fire retardancy was evaluated using UL-94 testing, where the composite exhibited self-extinguishing behavior, reduced flame propagation, and no dripping characteristics due to APP-induced char formation. Morphological analysis using scanning electron microscopy (SEM) revealed strong fiber–matrix adhesion with limited interfacial debonding, while Energy Dispersive X-ray Spectroscopy (EDS) confirmed the uniform distribution of phosphorus-rich APP within the matrix and char layer. The experimental findings demonstrate that the developed S2 glass/phenolic/APP composite provides an effective balance between mechanical integrity and fire resistance, making it suitable for advanced fire-resistant structural panel applications.