user7648: I heard that when Buddha was asked about God, he kept silent. 
Although perhaps in Buddhism nothing really exists, did Buddha ever deny the existence of God?
Hasn't he really never spoken about God?

user-1: The Pali Canon refers to "God" (as distinct from gods) in several places. When the Buddha became enlightened, at first he hesitated to teach others, because he thought that his realization was too subtle and profound for others to understand. Recognizing what a great loss this would be to the world, God (in the form of Sahampati, chief of the Brahma world) appeared to the Buddha and entreated him to teach, much as Ananda entreated the Buddha to admit women to the sangha. Sahampati was very happy when the Buddha relented, something very difficult for devas to do, because he earned a lot of merit by inducing the Buddha to teach. 
God is also mentioned in connection with a monastic's search for the place where the elements cease as I recall. The monastic concentrated his mind and travelled in his mental body to the Brahma world, where Brahma appears as a broken record, mindlessly affirming his own divinity much like the Wizard of Oz. Privately taking the monastic aside, the chief of the Brahma realm explained that he did not know the answer to the question and recommended that the monastic ask the Buddha.
Finally, the suttas explain that the notion of God arose as a result of the formation of a new universe, which appears out of a state of potentiality after the collapse of the previous universe. The first being to be reborn in such a universe sees that he is the first such being and the delusion arises in him that he is the creator of the universe. Subsequent beings are reborn as well, and they see that there was a first being, and the delusion arises in them that he is God. This is how religion (= theisim) arises.
One need not take these stories literally or historically to realize that they communicate real underlying theological ideas. 

user8157: Here: Tittha Sutta: Sectarians

Monks, there are these three sectarian guilds that — when cross-examined, pressed for reasons, & rebuked by wise people — even though they may explain otherwise, remain stuck in [a doctrine of] inaction. Which three?
"There are brahmans & contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all caused by what was done in the past.' There are brahmans & contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all caused by a supreme being's act of creation.' There are brahmans & contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all without cause & without condition.


Also here: A Discourse to Knowers of Veda -- Tevijja Sutta

“And just even so, VāseMMha, though you say that the Brahmans are not able to point out the way to union with that which they have seen, and you further say that neither any one of them, nor of their pupils, nor of their predecessors even to the seventh generation has ever seen Brahmā. And you further say that even the Rishis of old, whose words they hold in such deep respect, did not pretend to know, or to have seen where, or whence, or whither Brahmā is. Yet
  these Brahmans versed in the Three Vedas say, forsooth that they can point out the way to union with that which they know not, neither have seen! Now, what think you, VāseMMha? Does it not follow that, this being so, the talk of the Brahmans, versed though they be in the Three Vedas, is foolish talk?”
VāseMMha, is there a single one of the Brahmans versed in the three Vedas who
  has ever seen Brahmā face to face?”


7648: <p>I heard that when Buddha was asked about God, he kept silent. </p>

<p>Although perhaps in Buddhism nothing really exists, did Buddha ever deny the existence of God?</p>

<p>Hasn't he really never spoken about God?</p>
 -1: <p>The Pali Canon refers to "God" (as distinct from gods) in several places. When the Buddha became enlightened, at first he hesitated to teach others, because he thought that his realization was too subtle and profound for others to understand. Recognizing what a great loss this would be to the world, God (in the form of Sahampati, chief of the Brahma world) appeared to the Buddha and entreated him to teach, much as Ananda entreated the Buddha to admit women to the sangha. Sahampati was very happy when the Buddha relented, something very difficult for devas to do, because he earned a lot of merit by inducing the Buddha to teach. </p>

<p>God is also mentioned in connection with a monastic's search for the place where the elements cease as I recall. The monastic concentrated his mind and travelled in his mental body to the Brahma world, where Brahma appears as a broken record, mindlessly affirming his own divinity much like the Wizard of Oz. Privately taking the monastic aside, the chief of the Brahma realm explained that he did not know the answer to the question and recommended that the monastic ask the Buddha.</p>

<p>Finally, the suttas explain that the notion of God arose as a result of the formation of a new universe, which appears out of a state of potentiality after the collapse of the previous universe. The first being to be reborn in such a universe sees that he is the first such being and the delusion arises in him that he is the creator of the universe. Subsequent beings are reborn as well, and they see that there was a first being, and the delusion arises in them that he is God. This is how religion (= theisim) arises.</p>

<p>One need not take these stories literally or historically to realize that they communicate real underlying theological ideas. </p>
 8157: <p>Here: <a href="http://www.accesstoinsight.org/tipitaka/an/an03/an03.061.than.html" rel="nofollow">Tittha Sutta: Sectarians</a></p>

<blockquote>
  <p>Monks, there are these three sectarian guilds that — when cross-examined, pressed for reasons, &amp; rebuked by wise people — even though they may explain otherwise, remain stuck in [a doctrine of] inaction. Which three?</p>
  
  <p>"There are brahmans &amp; contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all caused by what was done in the past.' <strong>There are brahmans &amp; contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all caused by a supreme being's act of creation.'</strong> There are brahmans &amp; contemplatives who hold this teaching, hold this view: 'Whatever a person experiences — pleasant, painful, or neither pleasant nor painful — that is all without cause &amp; without condition.</p>
</blockquote>

<hr>

<p>Also here: <a href="http://www.bps.lk/olib/wh/wh057.pdf" rel="nofollow">A Discourse to Knowers of Veda -- Tevijja Sutta</a></p>

<blockquote>
  <p>“And just even so, VāseMMha, though you say that the Brahmans are not able to point out the way to union with that which they have seen, and you further say that neither any one of them, nor of their pupils, nor of their predecessors even to the seventh generation has ever seen <strong>Brahmā</strong>. And you further say that even the Rishis of old, whose words they hold in such deep respect, did not pretend to know, or to have seen where, or whence, or whither Brahmā is. Yet
  these Brahmans versed in the Three Vedas say, forsooth that they can point out the way to union with that which they know not, neither have seen! Now, what think you, VāseMMha? Does it not follow that, this being so, the talk of the Brahmans, versed though they be in the Three Vedas, is foolish talk?”</p>
  
  <p>VāseMMha, is there a single one of the Brahmans versed in the three Vedas who
  has ever seen <strong>Brahmā</strong> face to face?”</p>
</blockquote>
