Kasajima (笠島) is a district located on the main island (Honjima) in the Shiwaku Islands archipelago in the Seto Inland Sea in Japan.

The city has been well preserved since the Edo period and was selected as a Groups of Traditional Buildings.

The most populated city in the Shiwaku Islands, Kasajima is located on Honjima. Until the Sengoku period, the islands were the main base of the Shiwaku water force. During the Edo period it was an important place in water transportation. The city focused on lighter cargo vessels and prospered, and it was then that the townscape was built. In the earlier part of the Edo period the city flourished, but later on there was a flood of people with the same skills, and so the city gradually declined. In 1720, on the decree of the bakufu, the sale of ships and vessels was turned over to workers in Osaka. After that the people of Kasajima leveraged their building skills by starting to build homes, and were soon well known throughout Japan. Several times a year the workers would return to Kasajima to do repairs there. It is for that reason that the town from that period is so well preserved.

In 1985 the town was selected as a traditional architectures preservation district, and the village is still being mended and preserved. Within the village, the stores that built and sold boats, as well as the homes of merchants are being promoted. Although it is a small town, the roads were built in a key shape for defensive purposes. Three estates are usually open to the public for observation.

• 地区名称：丸亀市塩飽本島町笠島
• 種別：港町
• 選定年月日：1985年4月13日
• 選定基準：伝統的建造物群及びその周囲の環境が地域的特色を顕著に示している
• 面積：13.1ha

• 塩飽本島町笠島伝統的建造物群保存地区 - 重要伝統的建造物群保存地区
• まち並保存センター（真木邸）
• ふれあいの館（小栗邸）
• 文書館（藤井邸）
• 専称寺 - 年寄吉田彦右衛門の墓は国の史跡（史跡「塩飽勤番所跡」の附指定）
• 笠島城跡 - 香川県指定史跡
• 長徳寺 - 木造阿弥陀如来坐像、木造釈迦如来坐像、楊柳観音画像、モッコク、天文在銘文字瓦及び絵瓦は丸亀市指定文化財
• 尾上神社
• 笠島港

• 遠見山
• 塩飽勤番所 - 国の史跡
• 木烏神社、千歳座
• 来迎寺
• 正覚院 - 木造観音菩薩三尊像と線刻十一面観音鏡像は国の重要文化財

• JR丸亀駅から徒歩5分の丸亀港からフェリー（本島汽船）に乗り35分で本島（泊港）着、徒歩25分
• JR児島駅から徒歩3分の児島港から旅客船（便数少ない）に乗り30分で本島（泊港）着、徒歩25分

Wikimedia Commons has media related to Category:Kasajima, Marugame.

• 笠島重要伝統的建造物群保存地区（丸亀市のサイト）

34°23′39.8″N 133°47′16.2″E / 34.394389°N 133.787833°E / 34.394389; 133.787833