Counties 4 Yorkshire is an English rugby union league at the tenth tier of the domestic competition for teams from Yorkshire. Club rugby in Yorkshire operates without promotion play-offs meaning that the top two teams are automatically promoted to Yorkshire 3 and the bottom two teams were relegated to Yorkshire 5 until the RFU made changes to the Yorkshire league structure. Each season a team from Counties 3 Yorkshire or Yorkshire 4 may be picked to take part in the RFU Junior Vase - a national competition for clubs at levels 9-12.

For the 2017-18 season, Yorkshire 4 was broken up into two regional leagues - Yorkshire 4 (North West) and Yorkshire 4 (South East) - while Yorkshire 5 ceased to exist. Teams from both Yorkshire 4 and 5 were transferred into the regional divisions depending on location. After the teams have played each other home and away, in February the clubs are reallocated into a Premier league and a Shield league for one further round of fixtures. The top four teams from each league play in the Premier and the other teams play in the Shield. The top two teams in the Premier league are promoted to Counties 3 Yorkshire.

Ahead of the new season a decision was taken to introduce 2XVs into the league(s), to dispense with the North / South designation and to split the clubs out into A and B & C divisions

Departing were champions Nestle Rowntree and runners-up York Railway Institute both promoted to Counties 3 Yorkshire A.

Departing were Maltby promoted to Counties 3 Yorkshire B

Departing were Hornsea, promoted to Counties 3 Yorkshire as champions.

Thirsk RUFC joined the league after getting relegated from Counties 3 Yorkshire last season.

Departing were Dearne Valley (champions) promoted to Counties 3 Yorkshire.