Erlangshen is a mythical figure well known to women and children in China throughout the ages. His beliefs originated in and flourished in Shu. Erlangshen was the god of water in ancient times, but his meaning varies. His origins are related to several ancient people, such as Li Bing, Li Bing's son Li Erlang, Zhao Yu, and Deng Xia.
Li Bing
Li Bing was the prefect of Shu (present-day Sichuan) during the Qin Dynasty. According to the Records of the Grand Historian and the Book of Han, Li Bing was the prefect of Shu during the reign of Emperor Xiao Wen of Qin. He tamed the floods for the people of the county, built the Li Du reservoir, and dug the Sanmen Canal, irrigating thousands of hectares of fertile land and enriching the people of the Western Sichuan Plain. The people were so grateful for his benevolence that they built a temple to worship him, and he was deified. Later, he was posthumously honoured as “King Da'an” and “King Yingshengling” by the Shu Kingdom. The temple dedicated to him was located in Daojiang County, Yongkang County. In the fifth year of the Song Dynasty's Kaibao period (972), the emperor ordered the temple to be repaired, and in the seventh year (974), it was renamed “King Guangze”. Later generations called him “Factory King” and worshipped him once a year. His story is recorded in the books “Customs”, “New Search for Gods” and “Huayang Guozhi”.
Li Erlang　　
Li Erlang was the second son of Li Bing. Zhu Xi's “Zhu Zi Yu Lei” from the Song Dynasty says: “The Erlang Temple at Gangkou in Shu was built by Li Bing in honor of his meritorious feat of opening the Li Dui. It was dedicated to his second son.” Chen Xiangyi's “Shudu Suishi” from the Qing Dynasty says: “The people of Shu worship the Erlang God and call him the Lord of Sichuan. His statue is elegant, and his attendants hold an eagle and a dog. It is said that he was Li Bing's son.” The Changshu County Gazetteer records that the son of Li Bing, the governor of Shu, built a temple to him because he had killed the water dragon in Dujiang, Shu. The temple originally worshipped Duke Du of Shu and was called the Temple of the Emperor Who Looks Upon the Land. Before 494 to 498 AD, Liu Jilian, the governor of Yixing, moved the Wangdi Temple to Pixian, and the original site was renamed Chongde Temple to worship Li Bing. In the early Song Dynasty, the statue of Li Bing's son Li Erlang was added to the temple. After Wang Jian seized control of Shu during the Five Dynasties (935-990), Li Bing and his son were successively enfeoffed as kings. During the Song Yuanfeng period (1078-1085), the Erlang Temple in Guankou was built. In the eighth month of the Jia 8th year (1063) of the Song Renzong period, Li Erlang was conferred the title of Hui Linghou and the title “Huguo Lingying Wang”. During the Zhenghe period of the Song Huizong period (1111-1118), he was conferred the title of “Zhaohui Xianling Zhenren”. According to the “Yijian Zhi” (A Record of Foreigners): The Chongde Temple in Yongkang County was the shrine of the Guankou god. The king was given the title of Wang, and a temple official was appointed to oversee the shrine. The people of Shu were very respectful of the god, and made regular offerings to it. Whenever they had a request to make, they would sacrifice a sheep, and the number of sheep sacrificed each year reached 40,000. In the first year of the Zhishun reign period of the Yuan dynasty (1130), Li Bing was posthumously honored as the King of Virtue, Broad Benevolence, and Brilliant Wisdom, and his son Li Erlang was posthumously honored as the King of Heroic Valor, Brilliant Mercy, Auspicious Manifestation, Benevolent Protection, and Benevolent Blessing. In the fifth year of the Yongzheng reign period of the Qing dynasty (1727), Li Bing was posthumously honored as the King of Prosperity, Benevolence, and Benevolent Protection, and Li Erlang was posthumously honored as the King of Accomplished Deeds, Broad Benevolence, and Brilliant Brilliance. Therefore, the temple was later renamed the Temple of the Two Kings and is located in Dujiangyan City, Sichuan Province.
Zhao Yu was a Daoist priest in the Sui Dynasty. According to Liu Zongyuan's “Longcheng Lu” (Record of the Dragon City), Zhao Yu, whose style name was Zhongming, and his brother Mian both hid in Qingcheng Mountain and studied the Daoist way from the Daoist priest Li Yu. The Sui Emperor Yang knew of their virtue and made Zhao Yu the prefect of Jiazhou. At the end of the Sui Dynasty, when there was chaos in the world, Zhao Yu abandoned his post and hid, and his whereabouts are unknown. The Suzhou Prefecture Records say that when Zhao Yu was the prefect of Jiazhou in Sichuan, he encountered a water dragon and courageously went into the water to kill it, thus ridding the people of a major scourge. After his death, the Jialing River rose in flood, and the people of Sichuan missed him. Zhao Yu then rode a white horse in the mist, with a catapult and hunting dog, and crossed the river. A temple was built in Guankou to commemorate him, and he was called Erlang of Guankou. During the reign of Emperor Taizong of the Tang Dynasty, he was conferred the title of the Valiant General, and during the reign of Emperor Zhenzong of the Song Dynasty, he was posthumously conferred the title of the True Lord of the Wonderful Dao of the Pure Source. In the extant Yuan and Ming Dynasty's rare copy of the Zaju opera, there are three plays that feature Erlangshen: Erlangshen Drunk and Shooting the Magic Mirror, Erlangshen Subduing the Monkey King, and Erlangshen of Guankou Beheading the Bull-Calf Monster. Erlangshen refers to Zhao Yu in all of these plays.
Deng Xia
Deng Yi is the Erlangshen mentioned in the “Book of the Integration of Ancient and Modern Books: The Divine and the Strange”. The book records that there is an Erlangshen Temple in Zhongqing, and the deity worshipped there is Deng Xia. Deng Xia, courtesy name Yingyuan, was from Chen County. He was brave and strong from an early age, and his spirit was above his peers. The locals compared him to Fan Kuai of the Warring States period. He once followed Huan Wen and went on many expeditions, repeatedly achieving miraculous feats and becoming a famous general of his generation. Legend has it that there was a dragon in the water north of Xiangyang City that repeatedly killed people. Deng Yisui then fought the dragon and beheaded it, putting an end to the water disaster. The locals felt his grace and honored him as Erlang, building a shrine to worship him.
In short, the legends of Erlangshen are all related to water and stem from Li Bing's flood control. Successive emperors have bestowed many titles on Erlangshen and built temples to worship him, making it gradually become a folk custom. Since the Ming and Qing dynasties, the folk have often regarded the Prince of the Orient as the god of fire, while Erlangshen of Guankou as the god of water. The festival is held on the 24th day of the sixth lunar month every year. Gu Lu's “Qing Jialu” volume 6 says: The 24th day of the sixth lunar month is Erlangshen's birthday. Those suffering from sores pray at the temple inside the Wei Gate, and a white rooster is always sacrificed to him. In the past, apart from Sichuan, Erlang temples were built in many places across the country. Whenever there was a flood, prayers were offered to Erlangshen, and it was said to be very effective.

二郎神为中国历代妇孺皆知的神话人物，其信仰起源于蜀，也兴盛于蜀。二郎神世为水神，但其所指皆不尽相同，其来历与李冰、李冰之子李二郎、赵昱、邓遐等几位古人有关。
李　冰
李冰为秦朝蜀(今四川)郡守。据《史记》和《汉书》记载，秦孝文王时，李冰为蜀郡太守，为郡民治理水患，凿离堆，穿=三，灌溉万顷良田，使川西平原去患致富。民感其恩泽，立庙祭祀，使其神化。后蜀封为“大安王”，又封为“应圣灵王”。祀奉他的庙在永康郡导江县。宋开宝五年(972年)诏修其庙，七年(974年)改号“广泽王”。后世遂称厂济王，每岁一祀。《风俗通》《新搜神记》《华阳国志》等书中均有记载。
李二郎　　
李二郎为李冰之次子。宋代朱熹的《朱子语类》云：“蜀中灌口二郎庙，当时是李冰因开离堆有功立庙，乃是他第二子。”清代陈祥裔《蜀都碎事》云：“蜀人奉二郎神，谓之川主。其像俊雅，侍从者擎鹰牵犬，盖李冰之子也。”《常熟县志》记载，蜀郡太守李冰之子曾除蜀郡都江之蛟孽，有水功，故立庙。该庙原来祭祀蜀王杜宁，名叫“望帝祠”。公元494至498年之前，益卅剌史刘季连将望帝祠迁至郫县，原址改祀李冰，命名“崇德庙”，宋朝初年增祀李冰之子李二郎像。从五代王建据蜀以后(935-990年)，李冰父子相继被敕封为王。宋元丰年问(1078-1085年)，民立灌口二郎神庙，宋仁宗嘉八年(1063年)八月，封李二郎为惠灵候，号“护国灵应王”。宋徽宗政和年间(1111-1118年)改封“昭慧显灵真人”。据《夷坚志》载：永康郡崇德庙乃灌口神祠，爵封王，置监庙官，蜀人事之甚谨，每时节献享。及因事有祈者，必宰羊，一岁至四万头。元至顺元年(1130年)封李冰为圣德广裕英惠王，其子李二郎为英烈昭惠灵显仁佑王，清雍正五年(1727年)敕封李冰渭敷泽兴仁通佑王，二郎神为“承绩广惠英显王”。故后来改其祠为二王庙，今址在四川省都江堰市。
赵昱为隋朝道士。柳宗元《龙城录》云：赵昱，字仲明，与兄冕，俱隐青城山，从道士李钰学道。隋炀帝知其贤，起为嘉州太守。隋末天下大乱，赵昱弃官隐去，不知所终。《苏州府志》说，赵昱为四川嘉州太守时，遇有蛟患，于是奋勇入水斩而杀之，为民除了一大公害。他逝去后，嘉陵江水涨，蜀人思之，赵昱遂在雾中骑白马，夹弹弓，牵猎犬，于江上越流而过，因而在灌口建庙纪念，并称其为灌口二郎。唐太宗时封为神勇大将军，宋真宗追封为清源妙道真君，明代又加封为“赤城王”。现存的《元明孤本杂剧》中收有三剧《二郎神醉射锁魔镜》、《二郎神锁齐天大圣》、《灌口二郎斩犍蛟》其中的二郎神，均指赵昱。
邓　遐
邓遗为《古今图书集成·神异典》中所称二郎神。书中记载忠清里有二郎神庙，所奉神明为邓遐。邓遐，字应远，陈郡人。自幼勇力过人，气盖当时，乡人以战国樊哙喻之。曾经跟随桓温，多次外出征伐，屡立奇功，为一代名将。相传襄阳城北水中有蛟龙，屡害人性命，邓遗遂与蛟相斗，斩蛟，水患遂止。乡人感其恩泽，尊其为二郎，立祠祀之。
总之，二郎神的传说皆与水有关，源于李冰治水。历代帝王对二郎神多有加封，立祠祀之，使之逐渐成为民间风俗。明清以来，民间常以东岳炳灵太子为火神，而以灌口二郎神为水神。定于每年的农历六月廿四进行祭赛。顾禄《清嘉录》卷六云：六月廿四，为二郎神生日，患疡者拜祈于蔚门内之庙，祀之必以白雄鸡。 旧时除四川外，全国许多地方都还建有二郎庙，凡有水灾，必祈祷于二郎神，据说十分灵验。