Isabella Maria Susan Tod (18 May 1836 - 8 December 1896) was a women's rights campaigner and politician in Ireland.
She was born in Edinburgh and was educated at home by her mother, Maria Isabella Waddell, who came from County Monaghan. In the 1850s she moved with her mother to Belfast. She contributed to several newspapers, including the Northern Whig and the Dublin University Magazine.
She founded the North of Ireland Women's Suffrage Society which later became the Irish Women's Suffrage Society.
Along with Anna Haslam she campaigned for the repeal of the Contagious Diseases Acts. These acts allowed for state regulation of prostitutes in areas in which the British army was stationed. She was on the executive committee of the Ladies National Association for the Repeal of the Contagious Diseases Acts until 1889. After the Liberal Party split over the issue of Home Rule in Ireland she became an organiser of the Liberal Women's Unionist Association in Belfast.