Obsidian Energy Ltd. (previously known as Penn West Exploration Ltd., Penn West Petroleum and Penn West Energy Trust) is a mid-sized Canadian oil and natural gas production company based in Calgary, Alberta.

For a while it was one of the S&P/TSX 60, the sixty largest companies on the Toronto Stock Exchange. From 2005-2011 it was a Canadian royalty trust (CANROY), and reached a peak market capitalization in January 2008 of approximately US $9.5 billion.

The company experienced operational and financial difficulties when crude oil prices fell significantly in 2014. As a result, the company underwent a significant restructuring with the majority of the assets sold over the next two years to reduce debt.

Obsidian's oil and gas fields are located in Alberta, along the Western Canadian Sedimentary Basin, a region which is one of the world's largest petroleum reserves. Production comes from three key areas in Alberta: the Pembina Cardium, the Peace River oil sands, and the Alberta Viking. Total production in 2017 is expected to average approximately 31,000 bbl equivalent per day.

On 26 June 2017, Penn West Petroleum changed its name to Obsidian Energy.

Penn West Energy Trust paid a high dividend, yielding an annual rate of between 15 and 16% in early 2008; in addition, it paid out monthly, a relative rarity for equities listed on the New York Stock Exchange. Since the Trust's assets are considered a depletable resource, its dividend payments are not taxed at the regular dividend rate, but rather as return of capital instead of return on investment. This is an additional tax advantage in the United States, and applies to all royalty trusts.

At the Penn West shareholders annual general meeting in May 2015 company executives "admitted to accounting irregularities last year. The company said it currently faces six different lawsuits from investors in Canada and one consolidated lawsuit in the United States. More recently, the company was hit with a lawsuit regarding allegations of stock option manipulation."

Penn West was one of a group of oil and gas producers which also included Advantage, ARC Energy, Baytex Energy, Bonavista Energy, Bonterra, Canadian Oil Sands, Crescent Point Energy, Daylight Resources, Enerplus Resources, Enterra, Fairborne Energy, Freehold Royalty, NAL Oil & Gas, Paramount, Pengrowth, Peyto Energy, Progress Energy, Provident Energy, Trilogy, Vermillion Energy and Zargon Energy who did not pay "federal income taxes if they distributed their income to shareholders."

"The resulting double-digit dividend yields grabbed dividend investors’ attention in the mid-2000s. Eventually the government cracked down and starting in 2011, trusts were required to pay the same taxes as regular corporations. Consequently, all trusts converted to corporations, and many cut their dividends."

On January 1, 2011, Penn West converted from a CANROY to a conventional corporation.

In July 2014 Penn West's own newly appointed Chief Financial Officer David Dyck had discovered and reported irregularities in the company's accounting practices that "misclassified nearly $300-million in expenses."

Penn West had cut back its work force by almost 50% from late 2012 to June 2014. Penn West's profit in the second quarter of 2014 was $143-million, or 29 cents per share. Rick George who was Suncor's CEO from 1991 to 2012 served as Penn West's CEO from 2013 to 2014.

Penn West reported that preliminary findings revealed irregularities totaling "$381-million in 2013 and 2012." Penn West notified Canadian and U.S. regulators about the irregularities and expanded their own investigation to review results going back to 2007. Lawsuits tied to the accounting irregularities include those in Canada and a class action lawsuit in the United States. According to CBC News, by the end of July 2014, independent auditors contracted by Penn West to review its books uncovered that "$70 million worth of operating expenses that were reclassified as capital expenditures on things like property, plant and equipment in fiscal 2013; $110 million of similar expenses incorrectly classified in fiscal 2012; $100 million in operating expenses that were incorrectly reclassified as royalty expense" in 2012 and 2013.

The 2012, 2013, and 2014 financial statements were audited by KPMG LLP. KPMG was replaced by Ernst & Young LLP for the audit of the 2015 financial statements.

Since June 2013 Penn West began decreasing it workforce from 2,350 employees to fewer than 1,000. In response to the recent decline in oil prices, on September 2, 2015 Penn West Petroleum Ltd., announced cuts of about 400 full-time employees and contractors mainly from the company'a headquarters in Calgary which represents 35 per cent of the total workforce at Penn West.

Penn West also suspended "dividend payments to its shareholders after its next payment in October and reduc[ed] compensation for its board of directors."