Grimsby have parted company with boss Michael Jolley after a run of seven games without a win.
The 42-year-old was appointed manager at Blundell Park in March 2018.
He subsequently led them to safety in League Two before registering a 17th-place finish last season.
The Mariners said in a statement they "would like to place on record its thanks to Michael for his hard work and efforts since joining the club during a difficult period".
Jolley leaves with the club 18th in the fourth tier, six points above bottom-placed Morecambe.
He said in a statement posted on social media that it had been a "genuine privilege to work for such a fantastic club over the past 18 months".
Jolley worked in investment banking before taking on football coaching roles with clubs including Crystal Palace, Nottingham Forest, Crewe Alexandra and Burnley.
Swedish top-flight side Eskilstuna appointed him manager in June 2017, with the club winless and bottom of the table, but he left after failing to keep them up.
Grimsby are the third League Two team to change manager in three days, after Carlisle United sacked Steven Pressley on Wednesday and Leyton Orient parted with Carl Fletcher on Thursday.