UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 For the quarterly period ended September 30, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 for the transition period from to Commission File Number 001-38103 JANUS HENDERSON GROUP PLC Jersey, Channel Islands (State or other jurisdiction of incorporation or organization) 201 Bishopsgate London, United Kingdom (Address of principal executive offices) 98-1376360 (I.R.S. Employer Identifi ...