Keyshawn Johnson has filed a lawsuit against NFL agent Chris Ellison … claiming the guy owes him nearly $1 million for helping funnel clients his way — but Ellison is adamant the allegations are untrue.

Johnson said in his suit, which was filed in Los Angeles last week and obtained by TMZ Sports, that he and Ellison struck a deal about a decade ago … in which the former New York Jets star agreed to push players to be represented by Ellison in exchange for a portion of the NFL contracts the athletes received.

According to the lawsuit, Johnson was to get one-third of the three percent commission Ellison ultimately made on the players’ salaries.

Johnson claims based on their agreement, Ellison should have forked over $962,335 … but he’s yet to pay — and now, Johnson’s suing to recoup the cash.

For Ellison’s part, he told TMZ Sports on Tuesday he denies all of the claims Johnson made in the suit.