The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE
OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8
Report for the Calendar Year or Quarter Ended: 12-31-2019
Check here if Amendment    Amendment Number:
This Amendment (Check only one.):    is a restatement.
   adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: Bain Capital Life Sciences Investors, LLC
Address: 200 Clarendon Street
Boston, MA  02116
Form 13F File Number: 028-18477

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:
Name: Adam Koppel
Title: Managing Dir. of Bain Capital Life Sciences Investors, LLC
Phone: 617-516-2000
Signature, Place, and Date of Signing:
/s/: Adam Koppel Boston,  MA 02-14-2020
[Signature] [City, State] [Date]
Bain Capital Life Sciences Investors, LLC is the general partner of Bain Capital Life Sciences Partners, LP, which is the general partner of Bain Capital Life Sciences Fund, L.P. The shares of common stock of Dynavax Technologies Corporation ("DVAX") included on the Information Table are as reported on the Schedule 13D filed by Bain Capital Life Sciences Fund, L.P. and BCIP Life Sciences Associates, LP on August 22, 2019 and reflect the exercise and conversion, as applicable, of securities convertible into or exercisable for shares of DVAX common stock held by such persons, after giving effect to the provisions of such securities that prevent the exercise or conversion of such securities if such persons would beneficially own more than 9.99% of the outstanding DVAX common stock following such exercise or conversion. As of December 31, 2019, such persons held an aggregate of 7,525,000 shares of DVAX common stock. The shares of common stock of Savara Inc ("SVRA") included on the Information Table are as reported on the Schedule 13D filed by Bain Capital Life Sciences Fund II, L.P. and BCIP Life Sciences Associates, LP on December 30, 2019 and reflect the exercise and conversion, as applicable, of securities convertible into or exercisable for shares of SVRA common stock held by such persons, after giving effect to the provisions of such securities that prevent the exercise or conversion of such securities if such persons would beneficially own more than 9.99% of the outstanding SVRA common stock following such exercise or conversion. As of December 31, 2019, such persons held an aggregate of 4,571,139 shares of SVRA common stock. The shares of common stock of X4 Pharmaceuticals, Inc. ("XFOR") included on the Information Table are as reported on the Schedule 13G filed by Bain Capital Life Sciences Fund, L.P., Bain Capital Life Sciences Fund II, L.P. and BCIP Life Sciences Associates, LP on December 9, 2019 and reflect the exercise and conversion, as applicable, of securities convertible into or exercisable for shares of XFOR common stock held by such persons, after giving effect to the provisions of such securities that prevent the exercise or conversion of such securities if such persons would beneficially own more than 9.99% of the outstanding XFOR common stock following such exercise or conversion. As of December 31, 2019, such persons held an aggregate of 1,250,000 shares of XFOR common stock.
Report Type (Check only one.):
X 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.)
   13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).)
   13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)
Form 13F Summary Page
Report Summary:
Number of Other Included Managers: 2
Form 13F Information Table Entry Total: 10
Form 13F Information Table Value Total: 670,536
(thousands)
List of Other Included Managers:
Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state “NONE” and omit the column headings and list entries.]
No. Form 13F File Number Name
1 28-18476 Bain Capital Life Sciences Partners, LP
2 28-18478 Bain Capital Life Sciences Fund, LP