Juliana or Julianne Grenier (died 1213×16) was the Lady of Caesarea, which she inherited from her brother, Walter II, upon his death between 1189 and 1191. When she inherited the lordship, it had recently been conquered by Saladin, but in September 1192 it was restored to her rule by the Treaty of Jaffa. The city and its fortifications, however, were not rebuilt in her lifetime.
Juliana was the only daughter of Lord Hugh of Caesarea and his wife, Isabelle. Her brother Walter seems to have granted her lands at Naplouse. The jurist John of Ibelin in his treatise on the Assises records a list of fiefs and the service they owed around 1184: a certain lady of Caesarea is said to have owed two knights' service for lands near Naplouse.
Juliana's first husband, Guy, was a brother of Walter II of Brisebarre, Lord of Beirut. They are first recorded as married in a royal charter of Baldwin IV in 1179. In 1183, Juliana and Guy, who were apparently with the royal court in Jerusalem at the time, consented to her brother's sale of the casale of Galilaea, near Caesarea, to the Order of the Hospital for 5,000 bezants. It is not known if Guy was alive when Juliana inherited her title, or if he ever held the title Lord of Caesarea jure uxoris, although the Lignages d'Outremer records that he did. He was the father of four of her children: Walter III, her successor; Bernard, who died without issue; Isabelle, who married Renaud de Caiphas, chamberlain of Jerusalem; and Bertha (Berte), who married Renaud de Soissons, marshal of Cyprus.