觀無量壽經 The Guan wuliangshou jing, the Sutra of the Meditation on the Buddha of Immeasurable Life, given the reconstructed Sanskrit title of Amitāyur-dhyāna-sūtra; 1 fasc., translated in 424 by Kālayaśas 畺良耶舎, believed to be of Central Asian origin. T 365.12.340c-346b. The catalog name is 佛説觀無量壽佛經, and it is also known as the 無量壽佛經, 無量壽佛觀經, 無量壽觀經, 十六觀經, and abbreviated as 觀經. There was reportedly one other translation, but it had been lost since 730. This is one of the three principal scriptures　三部經 of the Pure Land school 淨土宗. It is recorded as being a sermon delivered by Śākyamuni at the request of the Queen Vaidehī 韋提希 of Magadha, while her husband was imprisoned. This scripture teaches sixteen kinds of meditation 十六觀 as a means for attaining rebirth in the Pure Land. It concludes by saying that even the most sinful of people can attain this kind of rebirth by chanting the name of Amitābha Buddha 阿彌陀佛. This text was commented on profusely in East Asian Buddhism, the most important early commentary being that of Shandao 觀無量壽佛經疏, with others by Huiyuan 觀無量壽經義疏, Zhiyi 觀無量壽佛經疏, and Jizang 觀無量壽經義疏. It served as a fundamental teaching text for all later Pure Land master, including Tanluan, Daocho, and Hōnen 法然. Important modern research was done on the text by Takakusu Junjiro, who translated it with the Sanskrit title given above (1894).

全一卷。劉宋畺良耶舍譯。又稱觀無量壽佛經、無量壽佛觀經、無量壽觀經、十六觀經。略稱觀經。收於大正藏第十二冊。淨土正依三部經之一。內容敘述佛陀應韋提希夫人所請，示現西方極樂淨土，並說修三福、十六觀為往生法。
　唐代善導謂此經以觀佛三昧為宗，又以念佛三昧為宗。相對於淨影慧遠、嘉祥吉藏等諸師所立十六觀皆定善之說，而立十六觀之後三觀為九品之散善。又謂佛雖廣說定、散兩門之益，然佛意唯在專稱阿彌陀佛名號。又據下品下生之文（大一二‧三四六上）：「如是至心令聲不絕，具足十念，稱南無阿彌陀佛。」解釋無量壽經第十八願之「乃至十念」即指十聲稱佛，遂以散心稱名為一切善、惡凡夫得往生之正定業；日僧源空即依其所說，創立日本淨土宗。
　蓋此經屬於觀經之一，與觀佛三昧海經、觀普賢菩薩行法經、觀彌勒上生兜率天經、觀世音觀經等皆為同類型者，乃說觀彌陀、觀音、勢至等三聖及極樂淨土莊嚴之法。又於十六觀中，以第九阿彌陀佛真身觀為最重要之觀行，經題亦依之而立。
　有關此經之翻譯，諸經錄、僧傳說法不一。於出三藏記集卷四謂，此經之譯者不詳。梁高僧傳卷三，以此經於劉宋時由畺良耶舍譯出，僧含筆受；法經錄以下之諸經錄皆沿用其說。又歷代三寶紀卷四、卷七，於畺良耶舍之譯本外，另列舉東漢、東晉兩種譯者不詳之譯本。
　注釋本經之著作頗多，重要者有觀無量壽經義疏二卷（慧遠）、觀無量壽佛經疏一卷（智顗）、觀無量壽經義疏一卷（吉藏）、觀無量壽經疏四卷（善導）、觀無量壽佛經圖頌一卷（傳燈）、觀無量壽佛經約論一卷（彭際清）、觀無量壽經扶新論一卷（戒度）等，其中以唐代善導之觀無量壽經疏四卷，流通較廣。〔開元釋教錄卷一、卷五、新編諸宗教藏總錄卷