Guido de Summa (died 1151) was an Italian Cardinal.
Probably he was already a Cardinal-Deacon under Pope Innocent II and as such, he signed papal bulls between 12 January 1142 and 9 December 1143.
Certainly Pope Celestine II named him Cardinal-Priest of S. Lorenzo in Damaso in the consistory celebrated on 17 December 1143.
On 23 September 1149 Eugenius III consecrated him Bishop of Ostia; as such, he signed papal bulls from 6 November 1149 until 14 April 1150.
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