Exhibit 99.1

Magnachip Reports Results for Fourth Quarter and Year 2020

SEOUL, South Korea, February 17, 2021 — Magnachip Semiconductor Corporation (NYSE: MX) (“Magnachip” or the “Company”) today announced financial results for the fourth quarter and full-year 2020.

Commenting on the results for the fourth quarter of 2020, YJ Kim, Magnachip’s chief executive officer stated, “Magnachip’s Q4 results exceeded our expectations, capping off one of the most challenging years for any of us. Our Q4 results demonstrated counter-seasonal strength with a 14.5% sequential revenue growth and GAAP operating income margin of 6.4%, and Non-GAAP adjusted operating income margin of 10.7% driven by a strong ramp-up in 5G as well as effective cost management.”

Commenting on the full-year, YJ stated, “2020 was an exceptional year for Magnachip, despite the challenges presented by the pandemic. We entered MX 3.0, the exciting new chapter of growth, with a sharpened focus as a pure-play standard products company, renewed energy, and a clear mission of empowering our customers. Under MX 3.0, we set long-term financial targets that we would like to achieve by 2023. While we recognize the path will not always be a straight line, the exciting opportunities ahead of us only reinforce our confidence in our growth outlook. I am proud of and thankful for our amazing group of dedicated employees who continued to deliver extraordinary results in 2020.”

Q4 and 2020 Financial Highlights

2

Q1 2021 Financial Guidance

The COVID-19 global pandemic is not behind us and continues to reduce our forward visibility. Q1 is our seasonally low quarter, but the demand in most of our end markets remains very healthy. Currently, the industry is going through severe supply constraints. While we are leaving some demand unmet in Q1 due to supply constraints, we are working closely with our strategic customer and our foundry partners to address supply constraints, and we expect the supply situation to improve later in the quarter. While actual results may vary, Magnachip currently anticipates for Q1 2021:

Q4 2020 Earnings Conference Call

Magnachip will host a conference call at 5 p.m. Eastern Time on February 17, 2021. The conference call will be webcast live and also is available by dialing toll-free at 1-844-536-5472. International call-in participants can dial 1-614-999-9318. The conference ID number is 6298187. Participants are encouraged to initiate their calls at least 10 minutes in advance of the 5 p.m. Eastern Time start time to ensure a timely connection. The webcast and earnings release will be accessible at www.magnachip.com. A replay of the conference call will be available the same day and will run for 72 hours. The replay dial-in numbers are 1-404-537-3406 or toll-free at 1-855-859-2056. The access code is 6298187.

Safe Harbor for Forward-Looking Statements

Information in this release regarding Magnachip’s forecasts, business outlook, expectations and beliefs are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. These statements include statements about Magnachip’s future operating and financial performance, outlook and business plans, including first quarter 2021 revenue and gross profit margin expectations, and the impact of the COVID-19 pandemic, escalated trade tensions and supply constraints on Magnachip’s first quarter 2021 and future operating results. All forward-looking statements included in this release are based upon information available to Magnachip as of the date of

3

this release, which may change, and we assume no obligation to update any such forward-looking statements. These statements are not guarantees of future performance and actual results could differ materially from our current expectations. Factors that could cause or contribute to such differences include the impact of changes in macroeconomic and/or general economic conditions, including those caused by or related to the COVID-19 outbreak, recessions, economic instability and the outbreak of disease; the impact of competitive products and pricing; timely design acceptance by our customers; timely introduction of new products and technologies; ability to ramp new products into volume production; industry wide shifts in supply and demand for semiconductor products; industry and/or company overcapacity; effective and cost efficient utilization of manufacturing capacity; financial stability in foreign markets and the impact of foreign exchange rates; unanticipated costs and expenses or the inability to identify expenses which can be eliminated; compliance with U.S. and international trade and export laws and regulations by us and our distributors; change or ratification of local or international laws and regulations, including those related to environment, health and safety; public health issues, including the COVID-19 pandemic; other business interruptions that could disrupt supply or delivery of, or demand for, Magnachip’s products, including uncertainties regarding the impacts of the COVID-19 pandemic that may result in factory closures, reduced workforces, scarcity of raw materials and goods produced in infected areas, as well as reduced consumer and business spending affecting demand for Magnachip’s products due to government and private sector mandatory business closures, travel restrictions or the like to prevent the spread of disease; and other risks detailed from time to time in Magnachip’s filings with the SEC, including our Form 10-K filed on February 21, 2020, our Form 10-Qs filed on May 11, 2020, August 7, 2020 and November 6, 2020 (including that the impact of the COVID-19 pandemic, trade tensions and supply constraints may also exacerbate the risks discussed therein) and subsequent registration statements, amendments or other reports that we may file from time to time with the Securities and Exchange Commission and/or make available on our website. Magnachip assumes no obligation and does not intend to update the forward-looking statements provided, whether as a result of new information, future events or otherwise.

About Magnachip Semiconductor

Magnachip is a designer and manufacturer of analog and mixed-signal semiconductor platform solutions for communications, IoT, consumer, industrial and automotive applications. The Company provides a broad range of standard products to customers worldwide. Magnachip, with more than 40 years of operating history, owns a portfolio of approximately 1,200 registered patents and pending applications, and has extensive engineering, design and manufacturing process expertise. For more information, please visit www.magnachip.com. Information on or accessible through Magnachip’s website is not a part of, and is not incorporated into, this release.

4

MAGNACHIP SEMICONDUCTOR CORPORATION AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands of U.S. dollars, except share data) (Unaudited)

5

MAGNACHIP SEMICONDUCTOR CORPORATION AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

(In thousands of U.S. dollars, except share data)

(Unaudited)

6

MAGNACHIP SEMICONDUCTOR CORPORATION AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands of U.S. dollars)

(Unaudited)

7

MAGNACHIP SEMICONDUCTOR CORPORATION AND SUBSIDIARIES

RECONCILIATION OF OPERATING INCOME TO ADJUSTED OPERATING INCOME

(In thousands of U.S. dollars)

(Unaudited)

We present Adjusted Operating Income as supplemental measures of our performance. We define Adjusted Operating Income for the periods indicated as operating income adjusted to exclude (i) Equity-based compensation expense, (ii) Early termination and other charges, (iii) Inventory reserve related to Huawei impact of downstream trade restrictions, (iv) Expenses related to Fab 3 power outage and (v) Others. For the year ended December 31, 2020, Early termination and other charges eliminate $5,629 thousand, of which $4,422 thousand related to the reduction of workforce under a voluntary resignation program and non-recurring professional service fees and expenses incurred in connection with certain treasury and finance initiatives. During the same period, inventory reserve related to Huawei eliminates a net charge of $1,460 thousand that we recorded in relation to the U.S. Government’s export restrictions on Huawei, and expenses related to Fab 3 power outage eliminate $1,168 thousand related to the write-off of the damaged work in process wafers and charges for facility recovery. For the year ended December 31, 2019, others eliminates a $585 thousand legal settlement charge related to dispute with a prior customer and a legal expense related to the indemnification of a former employee, which was borne by us under a negotiated separation agreement during the three months ended March 31, 2019.

8

MAGNACHIP SEMICONDUCTOR CORPORATION AND SUBSIDIARIES

RECONCILIATION OF NET INCOME TO ADJUSTED EBITDA AND ADJUSTED NET INCOME

(In thousands of U.S. dollars, except share data)

(Unaudited)

We present Adjusted EBITDA and Adjusted Net Income as supplemental measures of our performance. We define Adjusted EBITDA for the periods indicated as EBITDA (as defined below), adjusted to exclude (i) Equity-based compensation expense, (ii) Early termination and other charges, (iii) Foreign currency loss (gain), net, (iv) Derivative valuation loss (gain), net, (v) Loss on early extinguishment of borrowings, net, (vi) Inventory reserve related to Huawei impact of downstream trade restrictions, (vii) Expenses related to Fab 3 power outage and (viii) Others. For the year ended December 31, 2020, Early termination and other charges eliminate $5,629 thousand, of which $4,422 thousand related to the reduction of workforce under a voluntary resignation program and non-recurring professional service fees and expenses incurred in connection with certain treasury and finance initiatives. During the same period, inventory reserve related to Huawei eliminates a net charge of $1,460 thousand that we recorded in relation to the U.S. Government’s export restrictions on Huawei, and expenses related to Fab 3 power outage eliminate $1,168 thousand related to the write-off of the damaged work in process wafers and charges for facility recovery. For the year ended December 31, 2019, others eliminates a $585 thousand legal settlement charge related to dispute with a prior customer and a legal expense related to the indemnification of a former employee, which was borne by us under a negotiated separation agreement during the three months ended March 31, 2019.

9

EBITDA for the periods indicated is defined as Income (loss) from continuing operations before interest expense, net, income tax expense (benefit) and depreciation and amortization. We prepare Adjusted Net Income by adjusting income (loss) from continuing operations to eliminate the impact of a number of non-cash expenses and other items that may be either one time or recurring that we do not consider to be indicative of our core ongoing operating performance. We believe that Adjusted Net Income is particularly useful because it reflects the impact of our asset base and capital structure on our operating performance. We define Adjusted Net Income for the periods as income (loss) from continuing operations, adjusted to exclude (i) Equity-based compensation expense, (ii) Early termination and other charges, (iii) Foreign currency loss (gain), net, (iv) Derivative valuation loss (gain), net, (v) Loss on early extinguishment of borrowings, net, (vi) Inventory reserve related to Huawei impact of downstream trade restrictions, (vii) Expenses related to Fab 3 power outage, (viii) GAAP and cash tax expense difference, (ix) Others and (x) Income tax effect on non-GAAP adjustments. For the year ended December 31, 2020, Early termination and other charges eliminate $5,629 thousand, of which $4,422 thousand related to the reduction of workforce under a voluntary resignation program and non-recurring professional service fees and expenses incurred in connection with certain treasury and finance initiatives. During the same period, inventory reserve related to Huawei eliminates a net charge of $1,460 thousand that we recorded in relation to the U.S. Government’s export restrictions on Huawei, and expenses related to Fab 3 power outage eliminate $1,168 thousand related to the write-off of the damaged work in process wafers and charges for facility recovery. For the year ended December 31, 2019, others eliminates a $585 thousand legal settlement charge related to dispute with a prior customer and a legal expense related to the indemnification of a former employee, which was borne by us under a negotiated separation agreement during the three months ended March 31, 2019.

10