During the 1998–99 Dutch football season, AFC Ajax competed in the Eredivisie.

Having waltzed to the title during the previous season, Ajax suffered a complete collapse this season to finish 6th, 23 points adrift of champions Feyenoord. This was the club's lowest finish since 1965. The club also suffered poor form in Europe, finishing bottom of their Champions League group stage. Manager Morten Olsen had paid for the club's poor form in December with his job; his replacement, promoted reserve-team coach Jan Wouters, was unable to reverse the team's fortunes but managed to lead Ajax to win the KNVB Cup.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply. Players may hold more than one non-FIFA nationality.

No. Pos. Nation Player 1 GK  NED Edwin Van Der Sar 2 DF  DEN Ole Tobiasen 3 DF  NED Danny Blind (captain) 4 DF  NED Frank de Boer 5 DF  NED Tom Sier 6 MF  NED Ronald de Boer 7 MF  NGA Tijani Babangida 8 MF  NED Richard Witschge 9 FW  NED Gerald Sibon 10 MF  FIN Jari Litmanen 11 MF  GEO Georgi Kinkladze 12 GK  NED Fred Grim 13 MF  NED Richard Knopper 14 FW  POR Dani 15 MF  NGA Sunday Oliseh

No. Pos. Nation Player 16 MF  DEN Jesper Grønkjær 17 FW  RSA Benni McCarthy 18 MF  POL Andrzej Rudy 19 DF  NED Mario Melchiot 20 MF  SUR Dean Gorré 21 DF  GHA Kofi Mensah[notes 1] 22 MF  NED Peter Hoekstra 24 FW  GEO Shota Arveladze 23 FW  BRA Wamberto 29 FW  ANT Brutil Hosé[notes 2] 34 MF  NED Andy van der Meyde 37 DF  NED Tim de Cler — DF  NED Quido Lanzaat — DF  NGA Christopher Kanu — FW  NED Kevin Bobson

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply. Players may hold more than one non-FIFA nationality.

No. Pos. Nation Player — MF  NED Martijn Reuser (on loan to Vitesse) — MF  ARG Mariano Juan (on loan to Racing)

No. Pos. Nation Player — MF  USA John O'Brien (on loan to Utrecht)

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply. Players may hold more than one non-FIFA nationality.

No. Pos. Nation Player — DF  NED Serginho Greene — DF  NED Mitchell Piqué

No. Pos. Nation Player — MF  NED Cedric van der Gun

• Wamberto - Standard Liège, August
• Georgi Kinkladze - Manchester City, £5,000,000
• Jesper Grønkjær - AaB, £3,500,000, July^[1]

• Edwin van der Sar - Juventus, approx. £5,000,000
• Ronald de Boer - Barcelona
• Mariano Juan - Racing, loan
• Michael Laudrup - retired
• Andriy Demchenko^{[notes 3]} - FC Metalurh Zaporizhya

Pos	Team v t e	Pld	W	D	L	GF	GA	GD	Pts	Qualification		OLY	CZG	POR	AJX
1	Olympiacos	6	3	2	1	8	6	+2	11	Advance to knockout stage		—	2–0	2–1	1–0
2	Croatia Zagreb	6	2	2	2	5	7	−2	8			1–1	—	3–1	0–0
3	Porto	6	2	1	3	11	9	+2	7			2–2	3–0	—	3–0
4	Ajax	6	2	1	3	4	6	−2	7			2–0	0–1	2–1	—

Croatia Zagreb v Ajax

16 September 1998	Croatia Zagreb	0–0	Ajax	Maksimir, Zagreb
		Report		Attendance: 33,000 Referee: Kim Milton Nielsen (Denmark)

Ajax v Porto

30 September 1998	Ajax	2–1	Porto	Amsterdam ArenA, Amsterdam
	Rudy 57' Litmanen 86' (pen.)	Report	Zahovič 68'	Attendance: 40,000 Referee: Piero Ceccarini (Italy)

Olympiacos v Ajax

21 October 1998	Olympiacos	1–0	Ajax	Spiridon Louis, Athens
	Alexandris 39'	Report		Attendance: 73,250 Referee: Manuel Díaz Vega (Spain)

Ajax v Olympiacos

4 November 1998	Ajax	2–0	Olympiacos	Amsterdam ArenA, Amsterdam
	Witschge 33' Gorré 88'	Report		Attendance: 45,000 Referee: Stefano Braschi (Italy)

Ajax v Croatia Zagreb

25 November 1998	Ajax	0–1	Croatia Zagreb	Amsterdam ArenA, Amsterdam
		Report	Šimić 68'	Attendance: 46,000 Referee: Marc Batta (France)

Porto v Ajax

9 December 1998	Porto	3–0	Ajax	Estádio das Antas, Porto
	Zahovič 54', 80' Drulović 73'	Report		Attendance: 15,000 Referee: Pierluigi Collina (Italy)