UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549
SCHEDULE 13G Under the Securities Exchange Act of 1934
Amendment No.: 0*
Name of Issuer: Atlassian Corporation plc
Title of Class of Securities: Class A Ordinary Shares

CUSIP Number: G06242104

Date of Event Which Requires Filing of this Statement: 12/31/2017

Check the appropriate box to designate the rule pursuant to which this
Schedule is filed.

[X] Rule 13d-1(b) [ ] Rule 13d-1(c) [ ] Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class
of securities, and for any subsequent amendment containing information
which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not
be deemed to be "filed" for the purpose of Section 18 of the Securities
Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of
that section of the Act but shall be subject to all other provisions of
the Act (however, see the Notes).

CUSIP No.: G06242104

1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE
PERSON Janus Henderson Group plc EIN #00-0000000

2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP a. ___ b. ___

3. SEC USE ONLY

4. CITIZENSHIP OR PLACE OF ORGANIZATION Jersey, Channel Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5. SOLE VOTING POWER 0**

6. SHARED VOTING POWER 7,224,883**

7. SOLE DISPOSITIVE POWER 0**

8. SHARED DISPOSITIVE POWER 7,224,883**

9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
7,224,883**

10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
N/A

11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.8%**

12. TYPE OF REPORTING PERSON IA, HC

** See Item 4 of this filing

CUSIP No.: G06242104

1. NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE
PERSON Janus Henderson Enterprise Fund 84-1202943

2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP a. ___ b. ___

3. SEC USE ONLY

4. CITIZENSHIP OR PLACE OF ORGANIZATION Massachusetts

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

5. SOLE VOTING POWER 5,128,645**

6. SHARED VOTING POWER 0**

7. SOLE DISPOSITIVE POWER 5,128,645**

8. SHARED DISPOSITIVE POWER 0**

9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
5,128,645**

10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
N/A

11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.5%**

12. TYPE OF REPORTING PERSON IV

** See Item 4 of this filing

Item 1. (a). Name of Issuer: Atlassian Corporation plc ("Atlassian")

(b). Address of Issuer's Principal Executive Offices:

Exchange House, Primrose Street London EC2A 2EG

Item 2. (a).-(c). Name, Principal Business Address, and Citizenship of
Persons Filing:

(1) Janus Henderson Group plc 201 Bishopsgate EC2M 3AE, United Kingdom
Citizenship: Jersey, Channel Islands

(2) Janus Henderson Enterprise Fund 151 Detroit Street Denver, Colorado
80206 Citizenship: Massachusetts

(d). Title of Class of Securities: Class A Ordinary Shares

(e). CUSIP Number: G06242104

Item 3.

This statement is filed pursuant to Rule 13d-1 (b) or 13d-2(b) and the
person filing, Janus Henderson Group plc ("Janus Henderson"), is a
parent holding company/control person in accordance with Section
240.13d-1(b)(ii)(G). See Item 4 for additional information.

Janus Henderson Enterprise Fund is an Investment Company registered
under Section 8 of the Investment Company Act of 1940.

Item 4. Ownership

The information in items 1 and 5 through 11 on the cover page(s) on
Schedule 13G is hereby incorporated by reference.

Janus Henderson has an indirect 97.11% ownership stake in Intech
Investment Management LLC ("Intech") and a 100% ownership stake in Janus
Capital Management LLC ("Janus Capital"), Perkins Investment Management
LLC ("Perkins"), Geneva Capital Management LLC ("Geneva"), Henderson
Global Investors Limited ("HGIL"), Janus Henderson Investors Australia
Institutional Funds Management Limited ("HGIAIFML") and Henderson Global
Investors North America Inc ("HGINA"), (each an "Asset Manager" and
collectively as the "Asset Managers"). Due to the above ownership
structure, holdings for the Asset Managers are aggregated for purposes
of this filing. Each Asset Manager is an investment adviser registered
or authorized in its relevant jurisdiction and each furnishing
investment advice to various fund, individual and/or institutional
clients (collectively referred to herein as "Managed Portfolios").

As a result of its role as investment adviser or sub-adviser to the
Managed Portfolios, Janus Capital may be deemed to be the beneficial
owner of 7,189,683 shares or 7.7% of the shares outstanding of Atlassian
Class A Ordinary Shares held by such Managed Portfolios. However, Janus
Capital does not have the right to receive any dividends from, or the
proceeds from the sale of, the securities held in the Managed Portfolios
and disclaims any ownership associated with such rights.

As a result of its role as investment adviser or sub-adviser to the
Managed Portfolios, Intech may be deemed to be the beneficial owner of
35,200 shares or 0.0% of the shares outstanding of Atlassian Class A
Ordinary Shares held by such Managed Portfolios. However, Intech does
not have the right to receive any dividends from, or the proceeds from
the sale of, the securities held in the Managed Portfolios and disclaims
any ownership associated with such rights.

Janus Henderson Enterprise Fund is an investment company registered
under the Investment Company Act of 1940 and is one of the Managed
Portfolios to which Janus Capital provides investment advice.

Item 5. Ownership of Five Percent or Less of a Class

Not applicable.

Item 6. Ownership of More than Five Percent on Behalf of Another Person

The Managed Portfolios, set forth in Item 4 above, have the right to
receive all dividends from, and the proceeds from the sale of, the
securities held in their respective accounts.

The interest of one person, Janus Henderson Enterprise Fund, an
investment company registered under the Investment Company Act of 1940,
in Atlassian Class A Ordinary Shares amounted to 5,128,645 shares or
5.5% of the total outstanding Class A Ordinary Shares.

These shares were acquired in the ordinary course of business, and not
with the purpose of changing or influencing control of the Issuer.

Item 7. Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on by the Parent Holding Company

Janus Capital, Intech, Perkins, Geneva, HGIL, HGIAIFML and HGINA are
indirect subsidiaries of Janus Henderson and are registered investment
advisers furnishing investment advice to Managed Portfolios.

Item 8. Identification and Classification of Members of the Group

Not applicable.

Item 9. Notice of Dissolution of Group

Not applicable.

Item 10. Certification

By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired in the ordinary course of
business and were not acquired for the purpose of and do not have the
effect of changing or influencing the control of the issuer of such
securities and were not acquired in connection with or as a participant
in any transaction having such purposes or effect.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true,
complete and correct.

JANUS HENDERSON GROUP PLC

By /s/ Bruce Koepfgen
Bruce Koepfgen, Head of North America
Date 2/13/2018

JANUS HENDERSON ENTERPRISE FUND

By /s/ Susan K. Wold
Susan K. Wold, Chief Compliance Officer
Date 2/13/2018

EXHIBIT A JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of
1934, the persons named below agree to the joint filing on behalf of
each of them of a Statement on Schedule 13G (including amendments
thereto) with respect to the Class A Ordinary Shares of Atlassian
Corporation plc and further agree that this Joint Filing Agreement be
included as an Exhibit to such joint filings. In evidence thereof, the
undersigned hereby execute this Agreement as of the 13th day of
February, 2018.

JANUS HENDERSON GROUP PLC

By /s/ Bruce Koepfgen
Bruce Koepfgen, Head of North America

JANUS HENDERSON ENTERPRISE FUND

By /s/ Susan K. Wold
Susan K. Wold, Chief Compliance Officer