UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Exact name of registrant as specified in its charter; State of Incorporation; Address and Telephone Number IRS Employer Identification No. 1-14756 Ameren Corporation 43-1723446 (Missouri Corporation) 1901 Chouteau Avenue St. Louis, Missouri 63103 (314) 621-3222 Commission File Number FORM 10-Q ý Quarterly report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the Quarterly Period Ended March 31, 2019 OR ¨ Tran ...

Table of Contents Exact name of registrant as specified in its charter; State of Incorporation; Address and Telephone Number IRS Employer Identification No. Commission File Number UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (X) Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the fiscal year ended December 31, 2018. OR ( ) Transition report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the transition p ...