Lantingji Xu, also known as Lanting Xu, Linhe Xu, Xitie and Lanting Shixu on the Third Day of the Third Lunar Month, is a running - script work by Wang Xizhi in the Eastern Jin Dynasty. On the third day of the third lunar month in the ninth year of Yonghe (353 AD), Wang Xizhi and his friends gathered at Lanting in Shanyin, Kuaiji. They drank wine and composed poems. Wang Xizhi compiled the poems written by everyone into Lanting Ji and wrote a preface for it, which is Lantingji Xu.

The preface is written in an elegant and flowing style, with unpredictable changes in the shapes of characters. It is unique and natural, and is known as the "Best Running - Script Work under Heaven". The full text is divided into two parts. The first part describes the time, place, activities and climate of the gathering, while the second part expresses the sentiment of the brevity and preciousness of life. Lantingji Xu has extremely high calligraphic, artistic and social values. It demonstrates Chinese traditional culture and has a positive guiding and exemplary effect on the forms and contents of literary gatherings in later generations.