That's a complicated question. What defines a nation? That's difficult to define even nowadays. Even if de facto some states exist and rule themselves, they are not considered sovereign nations due to diplomatic factors. There was no UN at the time, though there was already an idea of international law. So, to be a sovereign state in the XIXth century would mean not only to be independent and manage their own affairs, but to be recognized as independent by established nations and given recognition.

There is no doubt that the CSA existed as a sovereign nation as a matter of fact. They had effective control over a large territory, which was as large as European Russia, could make and enforce laws, had an army and navy, and had a constitution and a established legal system that could impart justice and even hold elections. The Lincoln administration never deviated from its official position that legally, the CSA did not exist. But, as William Gladstone pointed out, the Confederates "have made an army; they are making, it appears, a navy; and they have made what is more than either; they have made a nation."

But this, we've already established, is not enough for the world to consider the CSA to be a sovereign state. One of the big aims of Confederate diplomacy was obtaining the official recognition of Europe, mainly Britain and France. Official recognition carried with it many benefits that the Confederates were eager to obtain. Unfortunately for them, no nation even recognized and established formal relations, which would entail the opening of a consulate or a diplomatic mission in Confederate territory.

Lincoln had, early in the war, proclaimed the Confederates to be simple insurrectionists, and consequently a matter only of national interest. But his declaration of a blockade constituted an act of war that affected other nations. Under International Law, as set in the Treaty of Paris of 1856 (which the US did not sign), nations were not allowed to trade with a blockaded belligerent as long as the blockade was strong and effective. Otherwise, it was considered a "paper blockade" that need not be respected. The South was the center of the world's cotton production. Ending this trade obviously affected Europe, and the US was strong enough to enforce it despite Confederate attempts to claim otherwise. As a result, Britain issued a proclamation declaring its neutrality and recognizing the Confederates as a belligerent.

Government officials raised a hue and cry over this. As McPherson explains, "status as a belligerent gave Confederates the right under international law to contract loans and purchase arms in neutral nations, and to commission cruisers on the high seas with the power of search and seizure." This was not an official recognition of the Confederates as a nation, or a first step towards intervention as the Southerners hoped, but still, it recognized that a Confederacy did exist, which directly contradicted the assertions of the Lincoln administration. As Lord Russell points out, "The question of belligerent rights is one, not of principle, but of fact."

Britain's policy towards the Confederates was always lenient but uncommitted. They allowed Confederate envoys to travel to Britain, and they held conferences with Foreign Secretary Lord Russell. Seward was furious over this, and he sent a bellicose warning to the British. Luckily, the American minister plenipotentiary, Charles Francis Adams (the son of Presidents John Quincy and the grandson of John Adams) was more tactful, and he made his concerns heard to Russell, who assured him that he did not plan to meet with the commissioners anymore. The commissioners, among them the Fire Eater William L. Yancey, would resign soon and be replaced by ministers plenipotentiary. James Mason would go to London and John Slidell to Paris. This set in motion the well-known Trent affair.

I'll give a quick summary of the affair: the British ship on which Mason and Slidell were traveling, the Trent, was illegally stopped and searched by an US navy vessel, and both men were arrested. Britain was furious at this heavy handed affair, and demanded an apology. Listening to Lincoln's wise adage "one war at the time", the US government freed both Confederates, who reached Europe but did not achieve much.

The British also turned a blind eye to Confederate contracts for the construction of ironclads, or the presence of Confederate agents in London and cities such as Liverpool, which was seen as pro-South in sympathies. Palmerston was always unwilling to extend recognition and open actual diplomatic relations unless the Confederates had proven they would be able to achieve independence by themselves. He was against armed intervention, because war would gain so little to Britain despite the South's belief in "King Cotton". That is, they thought that the lack of cotton as a result of the Union blockade would force Britain to intervene, but the British found this arrogant. The South could only conquer diplomatic recognition through military victories, like the Continental Congress had done with France. And they hoped Antietam would be their Saratoga.

The Maryland Campaign followed many important Confederate victories. McClellan had been repulsed at the Seven Days, and the Federals were defeated at Second Manassas. Palmerston seemed to be more open to the possibility of recognizing the Confederacy and offering mediation, saying that should Lee achieve a great victory it would be time "for us to consider whether . . . England and France might not address the contending parties and recommend an arrangement upon the basis of separation?" Russell added that if the US refused, "we ought ourselves to recognise the Southern States as an independent State." And this is key. Even though they had been granted the status of belligerent power and been allowed to send commissioners, the Confederacy was not seen as a sovereign independent nation yet. They would have to actually end the war and remain independent for recognition to be extended.

The Confederates did have some friends within the British government. Gladstone and Russell, for reasons I admittedly can't completely discern, pushed for recognition several times. Bills to recognize the CSA were introduced many times - in a memorable occasion, a Member of Parliament introduced one and then mentioned that France would support recognition, so it was promptly voted down because the British did not want the "Frogs" to direct their foreign policy. Despite this, the Union victory at Antietam ended the hope for recognition, not permanently, that is certain, but the Confederacy would never again came as close as they did then. The Emancipation Proclamation also arouse pro-Union sentiments in Britain by many anti-slavery Britons.

It bears mentioning that France toyed with recognizing the Confederacy in exchange of help for their puppet regime in Mexico, but Emperor Napoleon III would not move forward without British backing. The Lincoln administration, worried with their invasion of Mexico, would redirect military operations to plant the flag in the border to supposedly send a warning to the French, who were actually not that impressed. Russia, for its part, was very pro-Union, and they quickly voted down a French proposal for offering mediation (after Antietam).

To summarize, the Confederacy was never recognized as a sovereign nation by the powers of the age. Though they did accord belligerent status to them, they were not willing to open actual diplomatic relations or help them directly unless the Southerners could prove that they were able to conquer their independence themselves. The South did come close, mainly at the Trent Affair and in their high mark around Antietam, but ultimately no foreign government recognized them as an actual sovereign state.

Sources: Mainly McPherson's Battle Cry of Freedom, which deals with this issue in chapter 18, John Bull's Virginia Reel (I love this title).

In short, no. The FAQ has a fairly comprehensive post on European reactions to the war by u/The_Alaskan, and there are lots of good books on this issue.

What Britain, and then, in imitation, the rest of Europe did starting in May, 1861, was recognize the Confederacy as a belligerent power. This is distinct from recognizing them as an independent, sovereign state, and was in line with international law (or, more properly, the law of nations) as understood in the mid-nineteenth century, where Grotius, Vattel, and Wheaton were the primary authorities. Rebellions or insurrections that achieved some nebulous level of size and success became subject to the laws of nations, with certain obligations and protections therein. So, even though the Queen officially declared Britain neutral in the contest and thereby recognized the belligerent status of the Confederacy, British officials were not permitted to meet with Confederate diplomats in any official capacity, and in their correspondence they usually followed Union practice by referring to the "so-called Confederate States."

The appointed [i.e., not local] governor of the Bahamas, Charles J. Bayley, for example told the Confederate "consul" (for lack of a better term) Lewis Heyliger through his colonial secretary that "His Excellency's [Bayley] instructions do not permit him to recognise any official representative of the Confederate States of America, but His Excellency will always be happy to receive any unofficial representations which you or any other gentleman of the Southern States may wish to offer him in his private and personal capacity." (Charles R. Nesbitt to Lewis Heyliger, 2 October 1862, CSA Records, reel 8, Library of Congress)

For context, the political elite of the Bahamas heavily favored the Confederacy, as did many of the Royal Navy officers on the North American station, and they and Bayley regularly socialized with Heyliger, other Confederate citizens, officials, and blockade runners in Nassau. Bayley, while not perhaps a partisan of the CSA, was quite racist even for the 1860s and made several public statements that got him rebuked by the Colonial Office for appearing un-neutral, but even he would not go so far as to meet with Heyliger, who was his acquaintance and perhaps even his friend, in a public capacity.

This mirrored the treatment the Confederacy's official representatives received in Britain. Lord Russell, the Foreign Secretary, and Lord Palmerston, the Prime Minister, met with Confederate representatives only in private and very briefly, and mostly refused entreaties to meet unless some extraordinary circumstances required it (such as in early 1865 when Russell summoned James Murray Mason to read him the riot act on Confederate raids from British territory in Canada). Confederate reps in some European capitals had a little more luck meeting with officials, but the other countries from France on down followed British the lead on this.

Sources: CO 23: Bahamas: Original Correspondence, UK National Archives

Confederate States of America Papers, Library of Congress, Manuscript Division

Kenneth Startup, "'This Small Act of Courtesy': Admiral Sir George Willes Watson, Trouble, Trials, and Turmoil in Bahama Waters," Journal of the Bahamas Historical Society vol. 31 (October 2009)

Augustus Charles Hobart-Hampden, Sketches from My Life, (New York: D. Appleton and Co., 1887)

Stephen Wise, Lifeline of the Confederacy: Blockade Running in the Civil War, U of South Carolina Press, 1988.

Howard Jones, Blue and Gray Diplomacy, UNC Press, 2009 (I think - working from memory here. Maybe 2010)