There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

Brown Advisory Sustainable Growth I (BAFWX Quick QuoteBAFWX - Free Report) : 0.64% expense ratio and 0.53% management fee. BAFWX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. BAFWX has achieved five-year annual returns of an astounding 13.68%.

Fidelity Advisor Semiconductors M (FELTX Quick QuoteFELTX - Free Report) is a stand out amongst its peers. FELTX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. With five-year annualized performance of 22.97%, expense ratio of 1.28% and management fee of 0.52%, this diversified fund is an attractive buy with a strong history of performance.

Principal Capital Appreciation R4 (PCAPX Quick QuotePCAPX - Free Report) . Expense ratio: 0.82%. Management fee: 0.44%. Five year annual return: 11.17%. PCAPX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.