The Championship strugglers made the announcement late on Monday night, two days after a 1-1 draw at Blackburn, Pulis’ 10th league match in charge.
Chairman Dejphon Chansiri said in a statement on the club website: “The performances and results have not been of the level expected since Tony Pulis was appointed. There are also other issues which have had a bearing on this decision.
“On the pitch, seven points from a possible 30 is not acceptable. It is vital we maintain our Championship status and I feel I must make a change now with over half of the season remaining to give us the best possible chance of doing so.”
Wednesday said first-team coach Neil Thompson would take charge of the team until a permanent appointment was made, starting with Tuesday’s game against Middlesbrough.
Former Stoke, West Brom and Middlesbrough manager Pulis was appointed on November 13 following the departure of Garry Monk but won just one match, a 1-0 victory at home to Coventry on December 19.
Wednesday lie second bottom of the table on 13 points, three points from safety.