Xcode 8.2•Swift 3.0.2

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var wv: UIWebView!
    override func viewDidLoad() {
        super.viewDidLoad()
        loadYoutube(videoID: "oCm_lnoVf08")
    }
    func loadYoutube(videoID:String) {
        guard
            let youtubeURL = URL(string: "https://www.youtube.com/embed/\(videoID)")
            else { return }
        wv.loadRequest( URLRequest(url: youtubeURL) )
    }
}

Xcode 7.3.1•Swift 2.x

import UIKit

class ViewController: UIViewController {
    // create an outlet for your webview 
    @IBOutlet weak var wv: UIWebView!
    override func viewDidLoad() {
        super.viewDidLoad()
        // load your you tube video ID
        loadYoutube(videoID: "oCm_lnoVf08")
    }
    func loadYoutube(videoID videoID:String) {
        // create a custom youtubeURL with the video ID
        guard
            let youtubeURL = NSURL(string: "https://www.youtube.com/embed/\(videoID)")
            else { return }
        // load your web request
        wv.loadRequest( NSURLRequest(URL: youtubeURL) )
    }
}