Margaret de Quincy, suo jure 2nd Countess of Lincoln (c. 1206 – March 1266) was a wealthy English noblewoman and heiress having inherited in her own right the Earldom of Lincoln and honours of Bolingbroke from her mother Hawise of Chester, received a dower from the estates of her first husband, and acquired a dower third from the extensive earldom of Pembroke following the death of her second husband, Walter Marshal, 5th Earl of Pembroke.

Her paternal grandfather, Saer de Quincy, 1st Earl of Winchester was one of the 25 sureties of the Magna Carta; as a result, he was excommunicated by the Church in December 1215.

[citation needed] On 23 November 1232, Margaret and her husband John de Lacy, Baron of Pontefract were formally invested by King Henry III as Countess and Earl of Lincoln.

Although he was nominally succeeded by their only son Edmund de Lacy (c.1227-1258) for titles and lands that included Baron of Pontefract, Baron of Halton, and Constable of Chester, Margaret at first controlled the estates in lieu of her son who was still in his minority and being brought up at the court of Henry III and Eleanor of Provence.

As the widowed Countess of Lincoln suo jure, Margaret was brought into contact with some of the most important people in the county of Lincolnshire.

This marriage, like those of his four brothers, did not produce any children; therefore when he died at Goodrich Castle on 24 November 1245, Margaret inherited a third of the Earldom of Pembroke as well as the properties and lordship of Kildare.

[8] As a result of her quarrels with her daughter, Margaret preferred her grandson Henry de Lacy who would become the 3rd Earl of Lincoln on reaching majority (21) in 1272.

She and her Italian daughter-in-law Alasia of Saluzzo shared in the wardship of Henry who was Margaret's heir, and the relationship between the two women appeared to have been cordial.