X/1106 C1, also known as the Great Comet of 1106, was a great comet that appeared on 2 February 1106, and was observed across the world from the beginning of February through to mid-March. It was recorded by astronomers in Wales, England, Japan, Korea, China and Continental Europe. It was observed to split into many pieces, forming the Great Comet of 1882 and Comet Ikeya–Seki as well as over 4000 small sungrazing comets observed by the SOHO space telescope. It is a member of the Kreutz Group, known as Subfragment I, a split from an earlier large (~150 km) comet that progressively fragmented under the influence of the Sun.
A brief note in the Welsh manuscript known as the Brut y Tywysogion reads:
[-1106]. Yn y vlwydyn honno y gwelat seren anryued y gwelet yn anuon paladyr oheuni yn ol y chefyn ac o prafter colofyn y veint a diruawr oleuat idaw, yn darogan yr hyn a vei rac llaw: kanys Henri, amherawdyr Rufein, gwedy diruawryon vudugolyaetheu a chrefudussaf vched y Grist a orffowyssawd. A'e vab ynteu, wedy cael eistedua amherodraeth Rufein, a wnaethpwyt yn amherawdyr.
This translates into English as:
[-1106]. In that year there was seen a star wonderful to behold, throwing out behind it a beam of light of the thickness of a pillar in size and of exceeding brightness, foreboding what would come to pass in the future: for Henry, emperor of Rome, after mighty victories and a most pious life in Christ, went to his rest. And his son, after winning the seat of the empire of Rome, was made emperor.
The 1106 annal of the Peterborough Chronicle describes the comet. The Dorothy Whitlock translation reads:
In the first week of Lent, on the Friday, 16 February, in the evening, there appeared an unusual star, and for a long time after that it was seen shining a while every evening. This star appeared in the south-west; it seemed small and dark. The ray that shone from it, however, was very bright, and seemed to be like an immense beam shining north-east; and one evening it appeared as if this beam were forking into many rays toward the star from an opposite direction.
The most impressive observations of the comet come from the Japanese chronicle Dainihonshi. The chronicle reported that on 7 February 1106 AD the gigantic comet appeared in the southwest and stretched across a massive portion of the sky towards the east. The brilliant comet was described as white and with a tail stretching 100 degrees across the entire sky. 
An excerpt from a Chinese manuscript describes the following report of a comet in 1106, mentioning the comet's breakup after perihelion, dated February 10:
In the reign of Hwuy Tsung, the 5th year of the epoch of Tsung Ning, the 1st moon [February], day Woo Seuh (Feb. 10th), a comet appeared in the west. It was like a great Pei Kow. The luminous envelope was scattered. It appeared like a broken-up star. It was 60 [degrees] in length and was 3 [degrees] in breadth. Its direction was to the north-east. It passed S.D. Kwei (southern Andromeda/northern Pisces). It passed S.D. Lew (Southern Aries), Wei (Pegasus), Maou, and Peih (Taurus). It then entered into the clouds and was no more seen.
The Vietnamese Annals Đại Việt sử ký toàn thư also recorded the comet event:
The source of these quotes is the edited version of the Chronicles by Thomas Jones, Brut y Tywysogyon, or, the Chronicle of the Princes: Red Book of Hergest version, University of Wales Press, Cardiff, 1955