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Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the following Registration Statements:

Registration Statement |  |
--- | --- | ---
Form |  | Number |  | Purpose
| S-8 |  |  | 33-27984 |  | Pertaining to Aon's savings plan
| S-8 |  |  | 33-42575 |  | Pertaining to Aon's stock award plan and stock option plan
| S-8 |  |  | 33-59037 |  | Pertaining to Aon's stock award plan and stock option plan
| S-3 |  |  | 333-50607 |  | Pertaining to the registration of 369,000 shares of common stock
| S-8 |  |  | 333-55773 |  | Pertaining to Aon's stock award plan, stock option plan, and employee stock purchase plan
| S-3 |  |  | 333-78723 |  | Pertaining to the registration of debt securities, preferred stock and common stock
| S-4 |  |  | 333-168320 |  | Pertaining to the registration of 4,545,566 shares of common stock registered on Post Effective Amendment No. 1
| S-4 |  |  | 333-57706 |  | Pertaining to the registration of up to 3,852,184 shares of common stock
| S-3 |  |  | 333-100466 |  | Pertaining to the registration as amended of 2,707,018 shares of common stock
| S-8 |  |  | 333-103344 |  | Pertaining to the registration of common stock
| S-8 |  |  | 333-106584 |  | Pertaining to Aon's deferred compensation plan
| S-8 |  |  | 333-145928 |  | Pertaining to the registration of common stock
| S-8 |  |  | 333-145930 |  | Pertaining to the registration of common stock underlying equity securities issued to Aon's president and chief executive officer
| S-3 |  |  | 333-159841 |  | Pertaining to the registration of debt securities, preferred stock, common stock, convertible securities, share purchase contracts, share purchase units and guarantees
| S-8 |  |  | 333-174788 |  | Pertaining to Aon's 2011 stock incentive plan and 2011 employee stock purchase plan
| S-8 |  |  | 333-178906 |  | Pertaining to Aon's savings plan
| S-4 |  |  | 333-178991 |  | Pertaining to the registration of 355,110,708 Class A Ordinary Shares of Aon Global Limited, and in the related Proxy Statement / Prospectus of Aon Global and Aon Corporation contained therein

of our reports dated February 24, 2012, with respect to the consolidated financial statements of Aon Corporation and the effectiveness of internal control over financial reporting of Aon Corporation, included in this Annual Report (Form 10-K) for the year ended December 31, 2011.

/s/ ERNST & YOUNG LLP

Chicago, Illinois
February 24, 2012

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Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM