Emperor Jin Aidi 晉哀帝 (r. 361-365), personal name Sima Pi 司馬丕, courtesy name Qianling 千齡, was a ruler of the Eastern Jin dynasty 東晉 (317-420). He was the oldest son of Emperor Cheng 晉成帝 (r. 325-342) and Lady Zhou 周氏, was Prince of Langya 瑯琊 and held the title of cavalry general (piaoji jiangjun 驃騎將軍). When his cousin Emperor Mu 晉穆帝 (r. 344-361) died, no heir apparent was in office. The Empress Dowager therefore issued a decree nominating Sima Pi heir of Emperor Mu.
On his accession to the throne in 361 therefore, Sima Pi had to grant his mother the title of Grand Consort (taifei 太妃). His own empress was Ms Mao 毛氏. Regency was carried out by Defender-in-chief (taiwei 太尉) Huan Wen 桓溫 (312-373). The latter's memorial to the throne of 362, proposing the transfer of the imperial seat back to the former capital Luoyang 洛陽 (which was actually occupied by the Former Yan empire 前燕, 337-370), roused anger and fear among the courtiers. Yet because it would be a vain declaration, Sima Pi agreed.
In the same year he reduced the field tax from 3 to 2 sheng 升 per mu 畝 (see weights and measures). Another measure to promote agricultural production and long-term tax revenue was the transformation of tax-exempted refugee households from the north into common households, which had to pay taxes.
In 363, the emperor's mother, who had resided in her son's former princely establishment, died, and Sima Pi decided to dedicate the customary two years of mourning for her (bengsang 奔喪), and therefore ordered Sima Yu 司馬昱, Prince of Guiji 會稽 and eventual Emperor Jianwen 晉簡文帝 (r. 371-372), to take over government affairs.
Sima Yi was an adherent of Daoist outer alchemy (liandan 煉丹) and poisoned himself by testing a pill of "immortality". He fell critically ill, so Empress Dowager Chu 太后褚 took over regency for him. He died in 361 and was buried in Mound Anping 安平陵. His posthumous title is Emperor Ai 哀 "The Deplorable" or "The Pitiful".
His successor was Sima Yi, who is known as the "Deposed Emperor" 晉廢帝 (r. 365-371).