Can you drive a rental car to Te Anau from Queenstown?

I'm trying to see if it is possible to do a reasonable day trip to the Milford Sound from Queenstown if I drive to Te Anau and then get a tour from there to see the Milford Sound? Does anyone know?

Kia Ora, Nature Girl.
Don't you dare attempt to drive the Milford Road, you'll do yourself a great disservice. As well as the very real possibility (no, more like probability) of coming to grief on this treacherous stretch of road, you will learn nothing whatsoever of the road, local history, geography, geology and interest points about the area. The drivers of the coaches that go on this road on a daily basis will talk to their passengers all the way and keep you informed. You don't get that in a car, not even if you are given the audio tapes that some rental companies issue.
The road from Te Anau to Queenstown is fairly good and should take about 2 and a half to 3 hours, but can be tricky at times. Like other people, I suggest the best way is to take a coach tour from Queenstown. You can break it in Te Anau if you want to and visit the glowworm caves of Te Ana Au, but it will mean an overnight stopover in Te Anau.
If you go on the tour from Queenstown be sure your trip includes the boat cruise on Milford Sound, and as has been suggested by others, on a fine day the flight back to Queenstown gives a different perspective to the return coach trip, but it will cost more.
A better tour if you can afford it is the overnight cruise on Milford Sound, a bit more expensive, but includes accommodation and activities like kayaking and seal watching.
An alternative is to visit Doubtful Sound instead of Milford Sound. Just as spectacular with the added advantage that there are far fewer Loopies in the trip - only about 100 instead of the 5000 that will be in Milford.. ( Loopie is the local term for a tourist.)
Also, don't be put off by the weather. Either sound in wet weather, is just as spectacular, or perhaps even more spectacular than in fine weather.
Google Miford Sound; you will find a variety of tour at a range of prices.

well I spose so

thats what cars are for - to drive them

You can get a return 1-day bus trip all the way from Queenstown to Milford, so why bother with a rental car? The bus trip takes about 12 hours and it's fairly exhausting, but at least somebody else does the driving. And it's cheaper than hiring a rental car.

Queenstown to Te Anau is on sealed roads. There is no reason why you should not drive a rental car there.

If you can afford it, fly one way at least. The scenery is unbelievable.

I would suggest a tour from queenstown. We had a rental car and just decided early one morning to drive to milford sound, it was so far away, the roads were terrible within the last 10kms, wet, icy, etc. We seemed to be the only car heading in that direction, heaps of cars and busses coming back from milford sound. when we finally arrived, starving from the huge drive, there was nothing there open and no tours operating.

Only got ourselves to blame as it was a spur of the moment trip. So go on a tour bus, the know the roads and the area, plus they tell you all of the highlights.

Full day tour - coach - cruise - coach is around $205.00 per adult.

Tours also available from Te Anau which will cost $127.00 per adult.

Travelling times;
Queenstown to Te Anau - 2hrs 45mins
Te Anau to Milford Sound - 2hrs 20mins

Return travelling times - 10hrs 10 mins - not including any cruising times.