Isabel Bigod, Lady of Shere, was an English noblewoman. She was the wife of Gilbert de Lacy, of Ewyas Lacy, and John FitzGeoffrey, Lord of Shere Isabel was born in Thetford, Norfolk in about 1212, the only daughter of Hugh Bigod, 3rd Earl of Norfolk, a Magna Carta surety, and Maud Marshal. Her paternal grandparents were Roger Bigod, 2nd Earl of Norfolk and Ida de Tosny, a former mistress of King Henry II of England. Her maternal grandparents were William Marshal, 1st Earl of Pembroke and Isabel de Clare, 4th Countess of Pembroke. She had four brothers including Roger Bigod, 4th Earl of Norfolk and Hugh Bigod. She also had two younger half-siblings John de Warenne, 7th Earl of Surrey and Isabelle de Warenne, by her mother's second marriage to William de Warenne, 6th Earl of Surrey.

Isabel's father had died in 1225. In 1225, the year of her father's death, Isabel married her first husband, Gilbert de Lacy, of Ewyas Lacy . He was the son of Walter de Lacy, Lord of Trim Castle and Ludlow Castle, and Margaret de Braose. Gilbert and Isabel's chief residence was Ewyas Lacy in Herefordshire; however, they spent the last two years of their marriage on his father's estates in Ireland, where their youngest child, Maud was born, and Gilbert would shortly afterwards die.

Together they had three children:

Walter de Lacy
Margery de Lacy , married before 14 May 1244 John de Verdun, Lord of Westmeath by whom she had issue.
Maud de Lacy , married firstly Pierre de Geneve, by whom she had issue; in 1252, she married secondly Geoffrey de Geneville, 1st Baron Geneville, Seigneur de Vaucouleurs, by whom she had two sons, Geoffrey de Geneville, and Sir Piers de Geneville, father of Joan de Geneville, 2nd Baroness Geneville.
Gilbert died on 25 December 1230 at Trim Castle, in County Meath, Ireland leaving Isabel a widow at the age of eighteen with three small children. Sometime before 12 April 1234, Isabel married her second husband, John FitzGeoffrey, Lord of Shere, Justiciar of Ireland.

The marriage produced six children:

Richard FitzJohn of Shere , married Margery Basset
Maud FitzJohn , married firstly Gerald de Furnivalle, Lord of Hallamshire; she married secondly William de Beauchamp, 9th Earl of Warwick, by whom she had issue.
Aveline FitzJohn , married Walter de Burgh, 1st Earl of Ulster, by whom she had issue including Richard Og de Burgh, 2nd Earl of Ulster.
Joan FitzJohn , married Theobald le Botiller http://freepages.family.rootsweb.ancestry.com/~otstott/ind299.html