OceanaGold : Reports Significant Increase in Mineral Resources at Waihi in New Zealand

MEDIA RELEASE

7 March 2019

OCEANAGOLD REPORTS SIGNIFICANT INCREASE IN MINERAL RESOURCES AT

WAIHI IN NEW ZEALAND

(MELBOURNE) OceanaGold Corporation (TSX: OGC) (ASX: OGC) (the "Company") is pleased to announce an updated Mineral Resource estimate for the Martha Underground Project (the "Project") and recent exploration results highlighting continued high-grade gold intersections at the Company's Waihi Gold Mine ("Waihi") located in New Zealand.

Highlights

• • Increased total Indicated Resource by 136% to 331,000 ounces of gold.

• • Increased total Inferred Resource by 97% to 667,000 ounces of gold.

Table 1: Updated Martha Project Mineral Resources

Resource Category	Cut-off	RESOURCES
Au g/t	kt	Au g/t	Au koz
Indicated	2.15	2,129	4.84	331
Inferred	2.15	4,522	4.59	667

Notes:

• - Resources are reported below the consented Martha Phase 4 open pit design,

• - Resources are constrained to within a conceptual underground designed based upon the incremental cut-off grade and at a gold price of NZD$2,142/oz.

• - No dilution is included in the reported figures and no adjustments have been made to allow for mining recoveries.

• - The tabulated resources are estimates of metal contained as troy ounces of gold and do not include allowances for processing.

• - All figures are rounded to reflect the relative accuracy and confidence of the estimates and totals may not add correctly.

• - There is no certainty that Mineral Resources that are not Mineral Reserves will be converted to Mineral Reserves.

Significant Drill Results

True Width	Gold Grade	Silver Grade	Location
(metres)	g/t	g/t
10.7	36.0	221.8	Harry-Empire Intersection
4.7	47.2	67.9	Royal Vein
16.5	10.1	17.1	Martha Vein
5.8	18.8	53.3	State Vein
8.8	10.6	121.0	Royal Vein
1.3	70.7	71.7	Martha Vein
6.1	14.8	60.2	Edward Vein
4.1	19.8	14.6	Dominion Vein

Mick Wilkes, President and CEO, "I am very pleased to announce a further increase to the mineral resource estimate for the Martha Underground Project. Over the past two years, we have made prudent investments in extensively drilling out the mineralised structures beneath the Martha Open Pit. Since that time, we have reported dozens of significant drill intercepts and a growing resource which has now culminated into an Indicated Resource of 331,000 ounces of gold and Inferred Resource of 667,000 ounces."

"The consenting (permitting) process was completed nearly a month ago and we continue to add significant resources as we seek to achieve our exploration targets. We are in the process of implementing the project development and mine plans. Once fully developed and ramped-up, production from the Martha Underground is expected to increase to recent historical levels while delivering significant socio-economic benefits to New Zealand."

Over the course of the next twelve to eighteen months, the Company will continue its extensive exploration program along the two underground drill drives to further discover and convert resources. The Waihi vein system is extensive and the primary structures such as the Martha, Empire, Edward and Royal veins are in part well defined. The exploration target is associated with these structures, however, additional veins, notably Dominion, State, Republic and Harry that are branches of and linking splays between these major veins are also returning high-grade intersections.

Following positive updates in August 2018 and October 2018 for the Martha Underground, drilling has continued at multiple drill locations extending 900 metres along two vertically separated underground drill drives (800m-drill drive and 920m-drill drive, Figure 1) and from several surface locations. These drives are advancing well with the breakthrough from the 920-drill drive to the Martha open pit now established and the 800-drill drive over 90% complete.

Since the commencement of the Martha Underground drill program, approximately 30,700 metres have been drilled to define mineralisation along sections of the Martha, Royal, Empire and Rex veins that support the geological and resource model. Following receipt of the Martha Underground consent, the focus of drilling with six underground rigs and two surface rigs is balanced between growing the Resource and converting areas to an Indicated Resource status sufficient to support feasibility studies and mine planning.

The intersection of high-grade mineralisation to date supports the exploration target reported in August 2018 with a potential volume of between 5 million and 8 million tonnes at a grade of between 4.0 g/t and 6.0 g/t gold. This exploration target is based on the assessment of surface and underground drilling data collected by the Company in addition to the significant amount of historical and archived geological and mining data from over a century of mining activity at Waihi. Exploration targets are conceptual in nature; there has been insufficient exploration to define a mineral resource of the potential volume and grade stated and that it isuncertain if further exploration will result in the target being delineated as a mineral resource of this size and grade.

Mick Wilkes added, "The recent drill results at Waihi continue to demonstrate the significant exploration potential at the Martha Underground. We will continue to invest in our extensive drill program from the two underground drill drives and have allocated a budget of over $11 million for 2019 to go with the $8 million planned spend for our newly discovered WKP prospect which we reported an initial resource of 234,000 ounces of gold in the Indicated category and 401,000 ounces of gold in Inferred Resources."

Figure 1 - Long Sectional Oblique View showing Martha Open Pit, Martha Underground, Main Target Areas

(pink) and Current Martha Underground Resource Areas (yellow).

Figure 2 - Plan View showing holes drilled from August 2017 to January 2019 within the Martha vein system and the dominant targeted veins (Martha, Empire, Royal, Edward). Pink = Main Target Areas, Yellow = Current

Martha Underground Resource Areas, Green = Recent and Current Mining Areas.

Table 2 - Significant Intersections from the Waihi Martha Underground Resource Drilling

Hole ID	East#	North#	Collar RL	Az#	Dip	From (m)	To (m)	True width (m)	Gold Grade (g/t)	Silver Grade (g/t)	Vein
	(metres)	(metres)	(metres)
800DC1RN1240	395901.9	643001.1	780.8	209.9	7.2	82.60	95.10	8.8	10.59	121.0	Royal
800DC1RN1245	395900.9	643001.1	779.4	226.6	-21.5	121.40	128.10	2.9	8.74	14.8	Royal
800DC1RN1246	395905.4	643002.2	778.6	127.4	-57.6	25.00	33.90	6.8	5.10	8.1	Royal
800SP1MR1214	395967.2	643097.5	778.7	290.7	-33.6	234.80	239.90	4.4	10.59	73.1	Martha
800SP1MR1214	395967.2	643097.5	778.7	290.7	-33.6	180.70	191.40	6.9	5.05	6.5	Dreadnought
800SP1MR1224	395967.2	643097.5	779.7	290.6	1.2	206.10	218.50	10.7	36.01	221.8	Harry-Empire
800SP1MR1224	395967.2	643097.5	779.7	290.6	1.2	159.40	163.75	4.2	15.99	37.7	Empire
800SP1MR1224	395967.2	643097.5	779.7	290.6	1.2	123.70	132.80	6.4	10.49	13.8	Dreadnought
800SP1MR1224	395967.2	643097.5	779.7	290.6	1.2	268.90	273.90	4.7	6.32	49.3	Martha
800SP1MR1258	395967.8	643098.3	779.2	304.6	-16.0	136.20	142.20	3.6	22.17	25.3	Dreadnought
800SP1MR1258	395967.8	643098.3	779.2	304.6	-16.0	188.70	201.20	10.8	4.72	10.7	Harry
800SP1MR1258	395967.8	643098.3	779.2	304.6	-16.0	205.00	213.20	8.2*	5.53	8.8	Harry-Martha
800SP1MR1269	395967.8	643098.1	779.0	300.7	-22.6	198.90	219.00	16.5	10.10	17.1	Martha
800SP1MR1277	395967.9	643098.4	779.9	311.0	6.3	148.50	149.30	0.8	61.10	73.3	Empire
800SP3MN1237	395989.8	643115.4	779.5	339.9	-12.6	187.80	192.90	4.1	19.84	14.6	Dominion
800SP3MN1237	395989.8	643115.4	779.5	339.9	-12.6	142.90	149.00	4.3	7.84	16.5	Empire
800SP3MR1221	395991.0	643115.3	779.9	8.7	-2.0	200.70	209.15	8.5*	13.26	208.4	Republic
800SP3MR1221	395991.0	643115.3	779.9	8.7	-2.0	200.70	203.20	2.3	15.16	59.3	Empire
800SP3MR1227	395990.8	643115.3	779.7	6.2	-8.1	236.10	253.80	13.6	5.84	10.1	Martha
800SP3MR1227	395990.8	643115.3	779.7	6.2	-8.1	196.00	197.10	0.9	28.90	33.3	Empire
800SP3MR1227	395990.8	643115.3	779.7	6.2	-8.1	183.00	187.65	3.7	6.95	11.5	Empire
800SP3MR1231	395991.1	643115.3	779.9	13.2	-2.6	206.70	216.00	7.8	7.24	28.9	Empire
800SP3MR1244	395990.6	643115.4	780.0	359.7	4.0	190.90	197.40	5.8	18.76	53.3	State
800SP3MR1248	395990.3	643115.5	779.3	353.0	-22.6	167.05	179.70	8.1	7.07	14.1	Empire
800SP3MR1248	395990.3	643115.5	779.3	353.0	-22.6	181.00	184.30	2.1	20.34	27.2	State
800SP3MR1248	395990.3	643115.5	779.3	353.0	-22.6	163.00	166.40	2.8	9.09	12.5	Dreadnought
800SP3MR1257	395990.5	643115.6	779.7	356.1	-7.1	187.50	197.20	8.4	4.53	4.6	State
800SP3MR1262	395990.7	643115.4	779.3	2.9	-14.0	202.40	207.20	4.6	12.00	13.7	State
800SP3MR1265	395991.2	643115.4	779.6	12.5	-7.7	208.20	214.00	3.6	18.32	38.7	Empire
800SP3MR1265	395991.2	643115.4	779.6	12.5	-7.7	255.30	261.35	5	7.72	9.8	Martha
800SP3MR1278	395989.5	643115.2	779.4	334.0	-16.3	141.10	145.40	4.2	12.89	20.6	Empire
920RCCRN1202	395746.7	642915.6	919.6	195.1	-12.5	67.00	69.30	2.2	21.88	27.6	Royal
920RCCRN1242	395747.0	642915.0	919.8	185.6	-4.3	69.55	71.00	1.3	25.91	247.5	Royal
920RCCRN1256	395747.6	642915.0	919.5	173.0	-6.8	71.10	75.50	4.3	7.94	50.4	Royal
920RCCRN1270	395749.4	642915.4	919.8	136.8	-3.5	101.80	107.35	4.7	47.17	67.9	Royal
920SP2MN1254	396156.3	643097.5	921.9	348.2	-27.0	309.95	313.40	2.1	21.05	15.3	State
920SP3MR1217	396038.3	643058.1	921.6	337.2	-6.8	355.20	356.80	1.3	70.70	71.7	Martha
920SP5MN1205	395810.5	642983.3	919.5	333.5	-0.6	292.10	296.50	3.4	22.71	32.9	Martha
920SP5MN1205	395810.5	642983.3	919.5	333.5	-0.6	298.30	303.10	3.4	9.34	9.7	Martha
920SP5MN1228	395809.6	642983.0	918.5	316.6	-24.2	166.50	171.20	4.7*	6.10	77.1	Boxall
920SP8GT1238	395480.7	642862.5	925.8	341.7	4.8	127.10	135.10	6.4	7.77	61.2	Empire
920SP9MN1264	395464.4	642833.2	925.6	267.1	-36.1	119.40	127.30	6.1	14.76	60.2	Edward