At 603,628 square kilometres (233,062 sq mi) and with a coastline of 2,782 kilometres (1,729 mi), Ukraine is the world's 44th-largest country (after the Central African Republic, before Madagascar). It is the largest wholly European country and the second largest country in Europe (after the European part of Russia, before metropolitan France). It lies between latitudes 44° and 53° N, and longitudes 22° and 41° E.

The Ukrainian landscape consists mostly of fertile plains (or steppes) and plateaus, crossed by rivers such as the Dnieper (Dnipro), Seversky Donets, Dniester and the Southern Buh as they flow south into the Black Sea and the smaller Sea of Azov. To the southwest, the delta of the Danube forms the border with Romania. Its various regions have diverse geographic features ranging from the highlands to the lowlands. The country's only mountains are the Carpathian Mountains in the west, of which the highest is the Hora Hoverla at 2,061 metres (6,762 ft), and the Crimean Mountains on Crimea, in the extreme south along the coast. However Ukraine also has a number of highland regions such as the Volyn-Podillia Upland (in the west) and the Near-Dnipro Upland (on the right bank of Dnieper); to the east there are the south-western spurs of the Central Russian Uplands over which runs the border with Russia. Near the Sea of Azov can be found the Donets Ridge and the Near Azov Upland. The snow melt from the mountains feeds the rivers, and natural changes in altitude form a sudden drop in elevation and create many opportunities to form waterfalls.

Significant natural resources in Ukraine include iron ore, coal, manganese, natural gas, oil, salt, sulphur, graphite, titanium, magnesium, kaolin, nickel, mercury, timber and an abundance of arable land. Despite this, the country faces a number of major environmental issues such as inadequate supplies of potable water; air and water pollution and deforestation, as well as radiation contamination in the north-east from the 1986 accident at the Chernobyl Nuclear Power Plant. Recycling toxic household waste is still in its infancy in Ukraine.

In the wake of the collapse of the Yanukovych government and the resultant 2014 Ukrainian revolution in February 2014, a secession crisis began on Ukraine's Crimean Peninsula which has a significant number of Russophone people. Unmarked, armed Russian soldiers began being moved into Crimea on 28 February 2014. On 1 March 2014, exiled Ukrainian President Viktor Yanukovych requested that Russia use military forces "to establish legitimacy, peace, law and order, stability and defending the people of Ukraine". On the same day, Russian president Vladimir Putin requested and received authorization from the Russian Parliament to deploy Russian troops to Ukraine and took control of the Crimean Peninsula by the next day. In addition, NATO was perceived by most Russians as encroaching upon Russia's borders. This weighed heavily upon Moscow's decision to take measures to secure its Black Sea port in Crimea. On 6 March 2014, the Crimean Parliament voted to "enter into the Russian Federation with the rights of a subject of the Russian Federation" and later held a referendum asking the people of these regions whether they wanted to join Russia as a federal subject, or if they wanted to restore the 1992 Crimean constitution and Crimea's status as a part of Ukraine. Though passed with an overwhelming majority, the vote was not monitored by outside parties and the results are internationally contested; it is claimed to have been enforced by armed groups which intruded and enforced voting according to their demands. On 11 March, the Crimean parliament and Sevastopol issued a letter of intent to declare independence from Ukraine as the Republic of Crimea and requested that they be admitted as constituents of the Russian Federation. On 16 March, they held the Crimean referendum on that issue. The next day, the U.S. and the European Union started sanctions against individuals who were 'undermining democratic processes and institutions in Ukraine' or were 'undermining the territorial integrity of Ukraine'.

On 18 March 2014, Russia and Crimea signed a treaty of accession of the Republic of Crimea and Sevastopol in the Russian Federation, though the United Nations General Assembly voted in favor of a non-binding statement to oppose Russian annexation of the peninsula.

At the end of February 2014, unrest also began in eight other eastern and southern oblasts (provinces) of Ukraine. In several cities in the Donetsk and Luhansk regions armed men, declaring themselves as local militia, seized government buildings, police and special police stations in several cities of the regions, and held unrecognized status referendums.

Talks in Geneva between the EU, Russia, Ukraine and USA yielded a Joint Diplomatic Statement referred to as the 2014 Geneva Pact in which the parties requested that all unlawful militias lay down the arms and vacate seized government buildings, and also establish a political dialogue that could lead to more autonomy for Ukraine's regions. When Petro Poroshenko won the presidential election held on 25 May 2014, he vowed to continue the military operations by the Ukrainian government forces to end the armed insurgency. More than 4,700 people have been killed in the military campaign. According to the United Nations, 730,000 Ukrainian refugees have fled to Russia since the beginning of 2014 and 117,000 have fled to other parts of Ukraine. As president-elect, Poroshenko promised to pursue the return of Crimea to Ukrainian sovereignty.

In August 2014, a bi-lateral commission of leading scholars from the United States and Russia issued the Boisto Agenda indicating a 24-step plan to resolve the crisis in Ukraine. The Boisto Agenda was organized into five imperative categories for addressing the crisis requiring stabilization identified as: (1) Elements of an Enduring, Verifiable Ceasefire; (2) Economic Relations; (3) Social and Cultural Issues; (4) Crimea; and, (5) International Status of Ukraine. In late 2014, Ukraine ratified the Ukraine-European Union Association Agreement, which Poroshenko described as Ukraine's "first but most decisive step" towards EU membership. Poroshenko also set 2020 as target for EU membership application.

In February 2015, after a summit hosted in Belarus, Poroshenko negotiated a ceasefire with the separatist troops. This included conditions such as the withdrawal of heavy weaponry from the front line and decentralisation of rebel regions by the end of 2015. It also included conditions such as the Ukrainian control of the border with Russia in 2015 and the withdrawal of all foreign troops from the Ukrainian territory. The ceasefire began at midnight on 15 February 2015. Participants in this ceasefire also agreed to attend regular meetings to ensure that the agreement is respected.