A new family of all‐carbon structures is proposed via substituting the sp² carbon atom in graphene and graphyne with carbon trigons. Owing to the existence of carbon trigons, these porous carbon allotropes are named as trigraphene and trigraphyne. The calculations of geometrical, vibrational, and energetic properties by density functional theory reveal that all these structures are metastable and dynamically stable. It is further disclosed from the electronic band structures that trigraphene and α‐trigraphyne are metal, while β‐trigraphyne and γ‐trigraphyne are semiconductor with indirect band gaps of 0.33 and 0.52 eV, respectively. Our results suggest a strategy to design new carbon materials with desired properties, and these all‐carbon materials would have many interesting applications once obtained.