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, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Fidelity Fund K (FFDKX Quick QuoteFFDKX - Free Report) : 0.37% expense ratio and 0.32% management fee. FFDKX 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. FFDKX has achieved five-year annual returns of an astounding 10.78%.

Goldman Sachs Flexible Cap R6 (GFCUX Quick QuoteGFCUX - Free Report) is a stand out amongst its peers. GFCUX 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. With five-year annualized performance of 10.52%, expense ratio of 0.58% and management fee of 0.55%, this diversified fund is an attractive buy with a strong history of performance.

Deutsche Science and Technology Institutional (KTCIX Quick QuoteKTCIX - Free Report) . Expense ratio: 0.69%. Management fee: 0.45%. Five year annual return: 12.91%. With a much more diversified approach, KTCIX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector.

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.