It is the first of 14 group matches as Yorkshire look to improve on a disappointing record in the game’s shortest form.
Since the competition was inaugurated in 2003, Yorkshire have only twice reached Finals Day, losing to Hampshire in the 2012 final and to Durham in the 2016 semi-final.
They failed to qualify for the knockout stages last year, finishing fifth in the North Group.
As ever, the fixtures against Lancashire are the ones that will attract particular interest.
Yorkshire entertain the old enemy at Headingley on Thursday July 25 before the return match at Old Trafford on Friday August 9.
Finals Day this year is later than ever, with the event being staged at Edgbaston on September 21.
Yorkshire Diamonds’ Kia Super League fixtures have also been announced.
The ladies kick-off their campaign at home to Surrey Stars on August 6, the first of 10 matches before Finals Day at Hove on September 1.
VITALITY T20 BLAST
Fri, Jul 19: v NOTTINGHAMSHIRE (Headingley)
Sat, Jul 20: v Derbyshire (Chesterfield)
Tue, Jul 23: v Leicestershire (Grace Road)
Thu, Jul 25: v LANCASHIRE (Headingley)
Sun, Jul 28: v Northamptonshire (Northampton)
Fri, Aug 2: v WORCESTERSHIRE (Headingley)
Sun, Aug 4: v BIRMINGHAM BEARS (Headingley)
Fri, Aug 9: v Lancashire (Old Trafford)
Sun, Aug 11: v DERBYSHIRE (Headingley)Y
Fri, Aug 16: v DURHAM (Headingley)
Fri, Aug 23: v Durham (Chester-le-Street)
Sun, Aug 25: v Nottinghamshire (Trent Bridge)
Thu, Aug 29: v NORTHAMPTONSHIRE (Headingley)
Fri, Aug 30: v Birmingham Bears (Edgbaston)
Wed, Sep 4-Sat Sep 7: Quarter-finals
Sat, Sep 21: Finals Day (Edgbaston)
YORKSHIRE DIAMONDS FIXTURES (Kia Women’s Super League)
Tue, Aug 6: v SURREY STARS (Headingley)
Sun, Aug 11: v LOUGHBOROUGH LIGHTNING (Headingley)
Tue, Aug 13: v Lancashire Thunder (Liverpool)
Thu, Aug 15: v WESTERN STORM (York)
Sun, Aug 18 v Loughborough Lightning (Loughborough)
Tue, Aug 20: v Surrey Stars (Guildford)
Wed, Aug 21: v Southern Vipers (Ageas Bowl)
Fri, Aug 23: v LANCASHIRE THUNDER (Scarborough)
Sun, Aug 25: v SOUTHERN VIPERS (York)
Wed, Aug 28: v Western Storm (Taunton)
Sun, Sep 1: Finals Day (Hove)