It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

T. Rowe Price Diversified Mid-Cap Growth (PRDMX Quick QuotePRDMX - Free Report) : 0.86% expense ratio and 0.64% management fee. PRDMX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. With annual returns of 11.13% over the last five years, this fund is a winner.

Neuberger Berman Genesis R6 (NRGSX Quick QuoteNRGSX - Free Report) is a stand out amongst its peers. NRGSX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. With five-year annualized performance of 10.03%, expense ratio of 0.74% and management fee of 0.71%, this diversified fund is an attractive buy with a strong history of performance.

Harbor Capital Appreciation Institutional (HACAX Quick QuoteHACAX - Free Report) . Expense ratio: 0.67%. Management fee: 0.6%. Five year annual return: 16.61%. HACAX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks.

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.