The Northern Cricket Union (NCU) Senior League is the provincial cricket league within the NCU jurisdiction in Ireland, which covers counties Antrim, Armagh, Down and south Tyrone of Northern Ireland. The league was formed in 1897 and is currently divided into four sections, namely the Premier League, Sections 1, 2 and 3. It is sponsored by Mercury Security & Facilities Management and marketed as the Mercury Premier League, Mercury Section 1, etc.

There are a total of 36 league members: 10 in the Premier League; 10 in Section 1; 8 in Section 2 and 8 in Section 3. There is promotion and relegation of one club between each division.

Teams play each other twice per season, once at home and once away, each season, with four points awarded for a win and two for a tie or for "no result". When two or more teams finish with the same number of points, the team with the best net run rate is placed highest. Matches consist of one innings per side, with a maximum of fifty, and a minimum of twenty overs bowled per innings.

Waringstown are the most successful side in the Premier League with 33 wins (6 shared). The current champions are Waringstown after winning the 2026 competition.

In 2020, the season was abridged due to the coronavirus pandemic and the Premier League was played as a single round of fixtures with the top four teams progressing to semi-finals and the champions declared after a final.

As of 2026, the clubs in the NCU Senior League included:^{[needs update]}

Source: Northern Cricket Union