"I am absolutely delighted. This is a great opportunity for me. I know it's a hard job, but what a job to start your managerial career with," O'Leary said.
"I am flattered to get a chance like this. I played all my career at the top with Arsenal and now I am starting as a manager at the top."
Ridsdale was relieved that he had got his man and said: "When we got off the plane from our game against Rome, we targeted David as the man we wanted to be manager.
"I felt on Friday we had a broad agreement with David's solicitor. We then sat down tonight, hammered out the finer points and when it was all agreed we opened a bottle of champagne."
The two-and-a-half year deal will be worth around pounds 600,000 per year to O'Leary - putting him in the top four or five highest-paid Premiership managers - and he has been guaranteed funds for transfers. The Irishman said last week that Leeds needed three top-quality players to compete with the likes of Arsenal and Manchester United.
"I had to be satisfied with promises about money for new players and I've got the guarantees I was looking for," the 40-year-old said.
"What I am looking for in the short term is for us to finish fifth in the league again as we did last season, so guaranteeing us a place in Europe, and reach a cup final. If we manage to do that then I shall be totally satisfied."
As for on the field activity the draw means Leeds have not registered a League victory since they overcame Southampton on 3 September.
Should they choose, Leeds and their followers could blame the refereeing eccentricities of Mike Reid, who brandished the yellow card an astonishing 13 times, with Chelsea earning it on eight occasions and Leeds five.
Yet that line of defence would obscure the fact that Leeds only had themselves to blame. If the hapless Reid simply overreacted on numerous occasions, then there was nothing wrong with his judgement when it came to adjudicating on the big decision of the match. He got it absolutely right when he awarded Leeds a penalty in first-half stoppage time when Michael Duberry grabbed Jimmy Hasselbaink.
The striker, though, made a mess of his spot-kick, firing straight down the middle, and Ed de Goey saved with his feet.
Although Franck Leboeuf's dismissal after 60 minutes was for a rough challenge on Harry Kewell, this was still no kicking match. Hence Gianluca Vialli's frustration with the referee, whom the Chelsea player-manager approached at half-time.
Later Vialli had cooled down, explaining: "Sometimes it is impossible not to complain about referees. They try to do their best.
"But I was complaining about a few decisions. I complained about the number of yellow cards, not just the ones involving our players, but Leeds' as well."
Leeds United (3-5-2): Robinson; Woodgate, Molenaar, Radebe; Hiden, Hopkin (Haaland, 72), Bowyer, McPhail, Granville, Kewell, Hasselbaink (Wijnhard, 80). Substitutes not used: Wetherall, Halle, Nuno Santos (gk).
Chelsea (4-3-3): De Goey; Ferrer, Leboeuf, Duberry, Babayaro; Wise, Desailly Di Matteo; Laudrup, Casiraghi (Flo, 76), Zola (Poyet, 66). Substitutes not used: Lambourde, Nicholls, Hitchcock (gk).
Referee: M Reed (Birmingham).
Bookings: Leeds: Bowyer, Molenaar, Hasselbaink, Wijnhard, Radebe. Chelsea: De Goey, Di Matteo, Leboeuf, Wise, Duberry, Babayaro. Sending off: Leboeuf.
Man of the match: Radebe.
Attendance: 36,292.Reuse content