自大型妄想，英语 : Grandiose delusions，是妄想症的一个分类，在各类精神疾病的患者中发现：包括三分之二的躁郁症患者(在躁狂状态的时候)，一半的精神分裂症患者和大部分物质滥用障碍的病人。自大型妄想的特点是拥有梦幻般的信念，相信自己是有名气的，无所不能的，富有的，或拥有很大的权力。妄想的内容通常像梦一般，特别是有一个超自然现象的，科幻小说的，或宗教的主题。相对于被害型妄想及幻听，自大型妄想较缺乏研究。约10％健康的人会有自大思想的经验，但不完全符合自大型妄想诊断的标准。

Grandiose delusions (GD) or delusions of grandeur are a subtype of delusion that occur in patients suffering from a wide range of mental illnesses, including two-thirds of patients in manic state of bipolar disorder, half of those with schizophrenia, patients with the grandiose subtype of delusional disorder, and a substantial portion of those with substance abuse disorders. GDs are characterized by fantastical beliefs that one is famous, omnipotent, wealthy, or otherwise very powerful. The delusions are generally fantastic and typically have a religious, science-fictional or supernatural theme. There is a relative lack of research into GD, in contrast to persecutory delusions and auditory hallucinations. About 10% of healthy people experience grandiose thoughts but do not meet full criteria for a diagnosis of GD.