Real-world affective faces refer to images of human faces captured in unconstrained, everyday environments that exhibit naturally occurring emotional expressions. Unlike faces recorded under controlled laboratory conditions with posed, prototypical emotions, standardized lighting, and fixed camera angles, real-world affective faces feature natural variations in head orientation, illumination, background, resolution, and partial occlusion. These visual representations capture the complexity of human emotion as it manifests in daily life, frequently displaying subtle, spontaneous, or compound emotional states rather than singular, exaggerated expressions, which makes them fundamental for developing and assessing facial expression recognition systems in practical, real-life applications.