In heraldry, the castle symbolizes strength, protection, authority, and enduring establishment, making it one of the most powerful architectural charges in armorial design. It often appears in coats of arms to represent defensive power, noble residence, or a family or community rooted in a place of strategic and historic importance. Because castles were both military strongholds and symbols of lordship, the charge can also suggest governance, prestige, and the responsibility to defend land and people.

Castles are especially common in the civic heraldry of towns and cities with fortified histories, and they appear prominently in the arms of regions and kingdoms, most famously in the arms of Castile, where the golden castle became a defining emblem. In heraldic design, the form of the castle, including its towers, gates, and masonry, can add layers of meaning related to openness, defence, and architectural identity. In heraldry, the castle remains a clear and dignified symbol of stability and power, expressing the idea that strength is not only a matter of force, but also of shelter, permanence, and the authority to protect what matters.