SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of June 2019

Commission File Number 001-12284

GOLDEN STAR RESOURCES LTD.

(Translation of registrant’s name into English)

150 King Street West

Suite 1200

Toronto, Ontario

M5H 1J9, Canada

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ¨            Form 40-F  x

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

 SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: June 3, 2019

EXHIBIT INDEX

Exhibit 99.1

Golden Star Reports Initial High Grade Extension Drilling Results from Prestea Underground Gold Mine and Project Update

Results Include 124.4 Grams Per Tonne of Gold Over 1 Metre

TORONTO, June 3, 2019 /CNW/ - Golden Star Resources Ltd. (NYSE MKT: GSS; TSX: GSC; GSE: GSR) ("Golden Star" or the "Company") is pleased to report the results from the 2019 extension and infill drilling program at its Prestea Underground Gold Mine ("Prestea Underground") in Ghana.

HIGHLIGHTS:

• Assay results for eight diamond drill ("DD") holes along the northern extension of the West Reef were received confirming ore body extensions to the north of the current reserves, approximately 150 metres ("m") along strike between 21 and 24 levels
• Significant intercepts in the northern extensions included:
• 1.10 m @ 37.71 grams per tonne ("g/t") Au from 169.9 m in hole WR24-262S01
• 1.00 m @ 124.4 g/t Au from 144.0 m in hole WR24-262S02
• 0.90 m @ 17.8 g/t Au from 157.2 m in hole WR24-262S03A
• The exploration program for the second quarter ("Q2") and the third quarter ("Q3") of 2019 will focus on further delineation of the mineralization in this area in order to potentially bring this material into the mine reserves
• Exploration will drill test the extents of the West Reef high grade shoot up and down-dip as well as along the plunge below 24 level and above 17 level during the fourth quarter ("Q4") of 2019

Northern West Reef Extension Drilling Program Results

Drilling commenced from a newly excavated northern drill chamber at the beginning of 2019 (X cut 262N) in the Prestea Underground 24 level. Eight holes have been completed to date in this drilling program, targeting the northern extension of the defined reserves. All holes intersected the West Reef structure, with several returning strong economic grades and widths.

These results confirm the extension of gold mineralization into this area and represent the opportunity to add new stopes, along strike of the current mining front, which have the potential to be mined during the next two years.

The drilling to date conducted from the 262 N X-cut totaled 2,700 m, and a further 5,000 m are expected to be completed before the end of Q3 2019.

Initially, drilling has targeted the West Reef structure at approximately 100 × 100 m centers.  In areas where economic widths and grades have been intersected, the drill spacing will be closed in to 25-30 m × 25-30 m to add confidence to the mineralization for conversion to an indicated mineral resource and subsequently to a probable mineral reserve, should the economics prove viable.

Once the infill, closer spaced drilling program has been completed in Q4 2019, the drilling plan will shift to further resource expansion drilling on a 100 × 100 m drill spacing targeting the West Reef down-dip below 24 level, and up-dip above 17 level. These drilling results will be used to update the inferred mineral resource base at Prestea Underground and, if successful, will be followed up on a tighter drill spacing in 2020. Results to date are encouraging and should the infill drilling convert these areas to indicated mineral resources, this could potentially add additional reserves in the immediate area of mining infrastructure on 24 level adding optionality and flexibility to the current mine plan as well as replacing depleted reserves.

Figures 1 and 2 show drill hole locations and can also be seen by following: http://files.newswire.ca/184/GoldenStarfig12.pdf

Figure 1: Prestea Underground Longsection (CNW Group/Golden Star Resources Ltd.)

Figure 2: West Reef Northern Extensions (CNW Group/Golden Star Resources Ltd.)

In-Fill Drilling Program Results

A definition drilling program in the current reserve areas of the Prestea West Reef ore body has also been ongoing to ensure adequate definition of the reserves for short to medium term planning prior to mining. The higher drilling density will enable better mine planning and stope design.

A total of 19 holes for 4,100 m have been completed in this program since drill results from Prestea were last reported, including Nine holes (2,900 m) drilled in 2019.   

Project Update

Development is complete on 11 Alimak raises, and stope blasting complete on the first eight stopes. The twelfth raise is complete and the thirteenth raise has advanced approximately 150 m and long hole drilling production is set up well to ensure that the ninth stope blasting was completed in May and the stope sequence will continue cascading to provide ore continuity in the second half of 2019.

Decline development has also recently begun on the 17 level to access the second panel of ore up-dip of the stopes currently being mined from the 24 level. This will ensure continuity of ore production once the ore on the 24 level is depleted.

Operational Review at Prestea Underground

As a result of the operational challenges the Company has faced at the Prestea underground mine, a request for tenders was initiated for a technical and operational review from various consulting firms. CSA Global has been contracted to begin this review with the mandate to take a holistic approach to understanding the problems facing the operation. All aspects of technical, operational and management areas will be examined in order for recommendations to be set forth to the Company for improvements at Prestea. The Company expects to communicate an update in Q3 of 2019.

APPENDIX

36 DD Results Reported June 3, 2019

Company Profile

Golden Star is an established gold mining company that owns and operates the Wassa and Prestea underground mines in Ghana, West Africa. Listed on the NYSE American, the Toronto Stock Exchange and the Ghana Stock Exchange, Golden Star is focused on delivering strong margins and free cash flow from its two high-grade, low cost underground mines. Gold production guidance for 2019 is 220,000-240,000 ounces at a cash operating cost per ounce of $620-$680. As the winner of the PDAC 2018 Environmental and Social Responsibility Award, Golden Star is committed to leaving a positive and sustainable legacy in its areas of operation.

Cautionary note regarding forward-looking information

Some statements contained in this news release are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995 and "forward looking information" within the meaning of Canadian securities laws. Forward looking statements and information include, but are not limited to, statements and information regarding: planned exploration in Q2 and Q3 of 2019; the ability to delineate mineralization in the drilled area to add new mineral resources to eventually convert into mineral reserves, which would add optionality and flexibility to the current mine plan and replace depleted reserves; planned further drilling of 5,000 m in the Northern West Reef Extension before the end of Q3 2019; planned exploration in Q4 2019 to drill test the extents of the West Reef high grade shoot up and down-dip as well as along the plunge below 24 level and above 17 level; the potential to mine areas drilled in the Northern West Reef Extension over the next two years; the intent to conduct a further 1,400 m of in-fill drilling in Q2 2019; the addition of new stopes at Prestea Underground which have the potential to be mined during the next two years; completion of ninth stope blasting in May 2019; belief that the stope sequence will continue cascading to provide ore continuity in the second half of 2019; and 2019 production guidance and cash operating cost per ounce guidance. Generally, forward-looking information and statements can be identified by the use of forward-looking terminology such as "plans", "expects", "is expected", "budget", "scheduled", "estimates", "forecasts", "intends", "anticipates", "believes" or variations of such words and phrases (including negative or grammatical variations) or statements that certain actions, events or results "may", "could", "would", "might" or "will be taken", "occur" or "be achieved" or the negative connotation thereof. Investors are cautioned that forward-looking statements and information are inherently uncertain and involve risks, assumptions and uncertainties that could cause actual facts to differ materially. There can be no assurance that future developments affecting the Company will be those anticipated by management. Please refer to the discussion of these and other factors in Management's Discussion and Analysis of financial conditions and results of operations for the year ended December 31, 2018, and our annual information form for the year ended December 31, 2018, each of which is filed on SEDAR at www.sedar.com. The forecasts contained in this press release constitute management's current estimates, as of the date of this press release, with respect to the matters covered thereby. We expect that these estimates will change as new information is received. While we may elect to update these estimates at any time, we do not undertake to update any estimate at any particular time or in response to any particular event.

Technical Information

The technical contents of this press release have been reviewed and approved by S. Mitchel Wasel, BSc Geology, a Qualified Person pursuant to National Instrument 43-101. Mr. Wasel is Vice President of Exploration for Golden Star and an active member and Registered Chartered Professional of the Australasian Institute of Mining and Metallurgy.

The results for Prestea Underground stated herein are based on the analysis of saw-split HQ/NQ diamond half core or a three kilogram single stage riffle split of a nominal 25 to 30 kg Reverse Circulation chip sample which has been sampled over nominal one meter intervals (adjusted where necessary for mineralized structures). Sample preparation and analyses have been carried out at SGS or Intertek Laboratories in Tarkwa, which are independent from Golden Star, using a 1,000 gram slurry of sample and tap water which is prepared and subjected to an accelerated cyanide leach (LEACHWELL). The sample is then rolled for twelve hours before being allowed to settle. An aliquot of solution is then taken, gold extracted into Di-iso Butyl Keytone (DiBK), and determined by flame Atomic Absorption Spectrophotometry (AAS). Detection Limit is 0.01 ppm.

All analytical work is subject to a systematic and rigorous Quality Assurance-Quality Control (QA-QC). At least 5% of samples are certified standards and the accuracy of the analysis is confirmed to be acceptable from comparison of the recommended and actual "standards" results. The remaining half core is stored on site for future inspection and detailed logging, to provide valuable information on mineralogy, structure, alteration patterns and the controls on gold mineralization

Additional information on earlier drilling results and Mineral Reserve and Mineral Resource estimates at Prestea are available in the Company's National Instrument 43-101 compliant Technical Report titled "NI 43-101 Technical Report on Resources and Reserves, Golden Star Resources, Bogoso/Prestea Gold Mine, Ghana" with an effective date of December 31^st, 2017.

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SOURCE Golden Star Resources Ltd.

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For further information: For further information, please visit www.gsr.com or contact: Tania Shaw, Vice President, Investor Relations and Corporate Affairs, +1 416 583 3800, investor@gsr.com

CO: Golden Star Resources Ltd.

CNW 16:00e 03-JUN-19