Robert de Ros, 1st Baron de Ros (c. 1223 - May 13, 1285), was an English nobleman and the first holder of the ancient title Baron de Ros.

He was grandson to Robert de Ros and Isabel Avenal, an illegitimate daughter of William I of Scotland and an elder Isabel Avenal. He was son to William de Ros d. 1264/1265) and Lucy Fitzpiers, daughter of Reginald FitzPiers, Lord of Blewleveney.

He was summoned to Parliament in 1264, during the reign of Henry III.

He was married to Isabel D'Albini, rich heiress of William Albini IV. They reportedly had eight children:

• William de Ros, 2nd Baron de Ros (1255 - 1317).
• Isabel de Ros (c. 1244 - June 12, 1356. Married de Fauconberge.
• Mary de Ros (1245 - May 23, 1326). Married William de Braose, son of John de Braose and Margaret ap Llewellyn. Margaret was a daugther of Llywelyn the Great.
• Joan de Ros (c. 1252 - October 13, 1348). Married John Lovell, 1st Baron Lovell of Tichmarch]].
• Avelina de Ros. Married Sir John de Bohun of Midhurst.
• Robert de Ros (1265 - 1361). Married "Ernberge".
• John de Ros, Bishop of Carlisle (d. 1332).
• Nicholas de Ros.

On July 3, 1257, Ros obtained from Henry III a grant of the free warren, in the lordship of Belvoir, by which the boundary was determined. In 1258, he was actively employed in Scotland, in delivering King Alexander III of Scotland out of the hands of his rebellious subjects; and at Chester, in resisting the hostile invasions of Llewelyn the Last. In the same year, he and his lady Isabel had a controversy with the Prior and Convent of Belvoir, relative to the right of presentation to the Church of Redmile (near Bottesford), which was amicably compromised by their relinquishing the patronage to the convent, for a certain compensation. In 1261 he obtained from the king the grant of a weekly market, to be held at Belvoir, on Tuesday; and of an annual fair on the feast of St John the Baptist, to continue for three days. In 1264, he was one of the insurgent barons who defeated Henry III at the battle of Lewes, and took him and the prince prisoner, confining them in Hungerford Castle. In 1264, de Ros was summoned to the parliament, which was called by the barons in the king's name. He died in 1285, and was buried at Kirkham.