Exhibit 23

Consent of Independent Registered Public Accounting Firm

The Board of Directors

Olin Corporation:

We consent to the incorporation by reference in the registration statements No. 333-216461 on Form S-3 and Nos. 333-18619, 333-39305, 333-35818, 333-97759, 333-110135, 333-110136, 333-124483, 333-133731, 333-148918, 333-158799, 333-166288, 333-176432, 333-195500, 333-209534, 333-211434, and 333-224569 on Form S-8 of Olin Corporation of our report dated February 24, 2020, with respect to the consolidated balance sheets of Olin Corporation as of December 31, 2019 and 2018, the related consolidated statements of operations, comprehensive income (loss), shareholders’ equity, and cash flows for each of the years in the three-year period ended December 31, 2019, and the related notes (collectively, the consolidated financial statements), and the effectiveness of internal control over financial reporting as of December 31, 2019, which report appears in the December 31, 2019 annual report on Form 10-K of Olin Corporation.

Our report refers to a change in the accounting method for leases due to the adoption of Accounting Standards Update 2016-02 - Leases and amendments thereto as of January 1, 2019.

/s/ KPMG LLP

St. Louis, Missouri

February 24, 2020