In January 2017, when Martin McGuinness resigned as deputy First Minister in protest against the Renewable Heat Incentive scandal, and said that he would not stand in the resulting snap election, O'Neill was chosen as Sinn Féin's new "party leader in the North".
The fact that she was favoured for the leadership ahead of former IRA member Conor Murphy marked a notable break in the leadership's direct association with the organisation.

In the election that followed McGuinness's resignation, O'Neill was returned to the Assembly, topping the poll in Mid Ulster and with a 20.6% share of first-preference votes.
In March 2017, she called for a referendum on the reunification of Ireland "as soon as possible" in response to the United Kingdom's decision to leave the European Union.
O'Neill led the Sinn Féin side in the inter-party negotiations that followed the election, aiming to restore a power-sharing coalition in Northern Ireland, but said at the end of March that the talks had failed, and Sinn Féin would not nominate her for the position of deputy First Minister.

In February 2018, O'Neill became vice president of Sinn Féin, succeeding Mary Lou McDonald who became president following the retirement of Gerry Adams.
In November 2019 she faced a leadership challenge from John O'Dowd, winning with 67% of the vote.

In January 2020, O'Neill was appointed deputy First Minister of Northern Ireland.
In January 2017, when Martin McGuinness resigned as deputy First Minister in protest against the Renewable Heat Incentive scandal, and said that he would not stand in the resulting snap election, O'Neill was chosen as Sinn Féin's new "party leader in the North". The fact that she was favoured for the leadership ahead of former IRA member Conor Murphy marked a notable break in the leadership's direct association with the organisation.
In the election that followed McGuinness's resignation, O'Neill was returned to the Assembly, topping the poll in Mid Ulster and with a 20.6% share of first-preference votes. In March 2017, she called for a referendum on the reunification of Ireland "as soon as possible" in response to the United Kingdom's decision to leave the European Union. O'Neill led the Sinn Féin side in the inter-party negotiations that followed the election, aiming to restore a power-sharing coalition in Northern Ireland, but said at the end of March that the talks had failed, and Sinn Féin would not nominate her for the position of deputy First Minister.
In February 2018, O'Neill became vice president of Sinn Féin, succeeding Mary Lou McDonald who became president following the retirement of Gerry Adams. In November 2019 she faced a leadership challenge from John O'Dowd, winning with 67% of the vote.
In January 2020, O'Neill was appointed deputy First Minister of Northern Ireland.
Michelle O'Neill